JP6750874B2 - Sheet feeding apparatus and image forming apparatus - Google Patents

Description

The present invention relates to a sheet feeding device for separating and feeding sheets, and an image forming apparatus including the sheet feeding device.

An image forming apparatus such as a copying machine or a printer is provided with a sheet feeding device that separates the stacked sheets one by one and feeds them toward the image forming unit in order to supply the sheets to the image forming unit. There is. The sheet is a recording medium on which an image such as plain paper, coated paper, or OHP is recorded.

2. Description of the Related Art Conventionally, as a separation method for a sheet feeding device, there is a retard roller separation method that includes a pickup roller that feeds stacked sheets, a feed roller that conveys the picked-up sheet, and a retard roller that faces the feed roller. .. In this retard roller separation system, the drive in the direction opposite to the sheet conveying direction is transmitted to the retard roller via a torque limiter (reverse drive system). The sheets fed by the pickup roller are separated and conveyed one by one between the feed roller and the retard roller (separation nip).

In the conventional sheet feeding device, there is a fixed system in which the sheet is stopped by using a torque limiter without transmitting the reverse drive to the retard roller, as opposed to the reverse drive system described above (see Patent Document 1).

The advantage of the reverse rotation drive method over the fixed method is that the return operation can be performed for a sheet that has passed a plurality of sheets because the separation nip where the feed roller and the retard roller face each other cannot be completely separated, and thus the separation performance is stable. On the other hand, the advantage of the fixed system over the reverse rotation drive system is that the drive mechanism for generating the reverse rotation drive can be omitted, so the cost can be reduced.

JP, 2000-159360, A

However, in the reverse rotation drive method, a returning force is not required when the sheet is conveyed between the feed roller and the retard roller, but the reverse rotation drive is applied to the retard roller. Therefore, an excessive load is applied to the torque limiter, which becomes a factor that shortens the life of parts such as the torque limiter.

On the other hand, in the fixed system, the returning operation cannot be performed on the sheets that have not been separated from the separation nip and have passed through a plurality of sheets. Therefore, there is a problem in that it is technically difficult to increase the transport speed and increase the types of sheets that can be handled.

Therefore, an object of the present invention is to provide a sheet feeding device that stabilizes the sheet separation performance (double feed resistance performance) and takes roller wear and component life into consideration.

To achieve the above object, the present invention provides a pickup roller that feeds a sheet placed on a placing portion, a feed roller that conveys the sheet fed by the pickup roller, and a feed roller that faces the feed roller. And a retard roller for separating the sheet into one sheet by a driving force transmitted from a driving source to rotate the pickup roller and the feed roller in the sheet conveying direction. Has a first drive transmitting means for rotating the retard roller in a direction opposite to the sheet conveying direction, and a one-way mechanism for transmitting only rotation of the retard roller in the sheet conveying direction. Second drive transmitting means for transmitting to the first drive transmitting means, wherein the first drive transmitting means is provided with the retard roller when the retard roller is loaded with a load equal to or more than a set value. The retard roller shaft has a torque limiter that does not transmit the rotation of the retard roller shaft in the direction opposite to the sheet conveying direction to the retard roller, and when the drive source is stopped, it is conveyed by a conveying member downstream of the feed roller in the sheet conveying direction. Rotation of the retard roller in the sheet conveying direction, which rotates along with the sheet, is transmitted to the first drive transmitting means via the second drive transmitting means, and the retard roller shaft is rotated in a direction opposite to the sheet conveying direction. It is characterized by rotating to.

According to the present invention, it is possible to provide a sheet feeding device that considers roller wear and component life while stabilizing the sheet separation performance (double feed resistance).

1 is a perspective view of a sheet feeding device according to a first exemplary embodiment. Drive conceptual diagram of the sheet feeding device in Embodiment 1 Control block diagram for controlling the sheet feeding device FIG. 3 is a perspective view of the sheet feeding device according to the second embodiment. Conceptual diagram for driving the sheet feeding apparatus according to the second embodiment Sectional view of an image forming apparatus including a sheet feeding apparatus

Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments should be appropriately changed depending on the configuration of the device to which the present invention is applied and various conditions. Therefore, unless otherwise specified, the scope of the present invention is not intended to be limited thereto.

[Example 1]
A sheet feeding apparatus and an image forming apparatus according to this embodiment will be described with reference to the drawings. First, the image forming apparatus will be described, and then the sheet feeding apparatus will be described.

(Description of image forming apparatus)
First, the overall configuration of an image forming apparatus including a sheet feeding device will be briefly described with reference to FIG. FIG. 6 is a diagram showing a schematic configuration of a full-color laser beam printer which is an example of an image forming apparatus including a sheet feeding device.

In FIG. 6, reference numeral 51 is a full-color laser beam printer (hereinafter referred to as printer), 51A is a printer main body which is an image forming apparatus main body, 51B is an image forming unit for forming an image on a sheet, and 70 is a fixing unit. Reference numeral 52 denotes an image reading device, which is an upper device installed substantially horizontally above the printer body 51A, and a discharge space P for discharging a sheet is formed between the image reading device 52 and the printer body 51A. .. Note that SF is a sheet feeding device to which the present invention is applied, which is provided below the printer main body 51A, and 65 is a toner cartridge.

The image information read by the image reading device 52 or the image information input from an external device such as a personal computer (not shown) is subjected to image processing, converted into an electric signal, and transmitted to the laser scanner 60 of the image forming unit 51B. .. Then, in the image forming unit 51B, the surface of the photosensitive drum 62 of each process cartridge 61 is scanned with laser light corresponding to the image information of the yellow, magenta, cyan, and black component colors emitted from the laser scanner 60. As a result, the surface of the photosensitive drum 62 whose surface is uniformly charged to a predetermined polarity and potential by the charger 63 is sequentially exposed, and yellow, magenta, and cyan are respectively transferred onto the photosensitive drums of the process cartridges 61. And a black electrostatic latent image is sequentially formed.

After that, the electrostatic latent image is developed with yellow, magenta, cyan, and black color toners to be visualized, and the primary transfer bias applied to the primary transfer roller 69 causes each color toner image on each photosensitive drum. Are sequentially superimposed and transferred onto the intermediate transfer belt 66. As a result, a toner image is formed on the intermediate transfer belt 66.

On the other hand, the sheet S sent out from the feeding cassette (depositing section) 80 provided in the sheet feeding device SF passes through the registration roller pair 90 and is constituted by the driving roller 66 a and the secondary transfer roller 67. Is sent to the secondary transfer unit. In the secondary transfer portion, the toner images formed by the image forming portion 51B are collectively transferred onto the sheet S.

Next, the sheet S on which the toner image is transferred in this manner is conveyed to the fixing unit 70, and is subjected to heat and pressure in the fixing unit 70, and is fixed to the sheet S as a color image. After that, the sheet S on which the image is fixed is discharged to the discharge space P by the first paper discharge roller pair 75a, and is stacked on the stacking portion 73 protruding on the bottom surface of the discharge space P.

(Explanation of sheet feeding device)
Next, the sheet feeding device SF in the image forming apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of a sheet feeding device SF according to this embodiment, and FIG. 2 is a drive conceptual diagram of the sheet feeding device SF.

A sheet feeding device (retard type feeding mechanism) SF for feeding a sheet will be described with reference to FIGS. 1 and 2. The sheet feeding device SF includes a pickup roller 1 for picking up the sheets S stacked in the feeding cassette 80, a feed roller 2 for conveying the picked-up sheets S, and a plurality of sheets facing the feed roller 2. A retard roller 3 that separates and conveys the sheet is provided.

Further, the sheet feeding device SF includes first drive transmission means and second drive transmission means. The first drive transmission means transmits the driving force from the drive motor M, rotates the pickup roller 1 and the feed roller 2 in the sheet conveying direction, and rotates the retard roller 3 in the direction opposite to the sheet conveying direction. The second drive transmission means has a one-way mechanism that transmits only the rotation of the retard roller 3 in the sheet conveyance direction, and transmits the rotation of the retard roller 3 in the sheet conveyance direction to the first drive transmission means. Hereinafter, the configuration of the sheet feeding device SF including the configuration of each drive transmission unit will be described.

The drive force of the feed roller 2 is transmitted from the drive motor M, which is a drive source that generates a drive force based on the feed signal, to the feed roller shaft 7 via the drive source gear 16. A driving force is transmitted from the feed roller shaft 7 to the pickup roller 1 via the transmission gears 11 and 12 and the pickup roller shaft 8 (first drive transmission means).

The rotation of the feed roller shaft 7 of the retard roller 3 is transmitted to the retard roller shaft 5 via the retard reverse rotation drive gear train 14, and the driving force is applied to the retard roller 3 in the reverse rotation direction (direction opposite to the sheet conveyance direction) via the torque limiter 4. Is transmitted (first drive transmission means).

The retard roller 3 is attached to the retard roller shaft 5 via a torque limiter 4. The retard roller 3, the torque limiter 4, and the retard roller shaft 5 are attached to a holder 19 and are configured to be swingable around a retard rotation shaft 6 held by a frame 17 adjacent to the retard roller shaft 5 as a swing center. There is.

The retard roller 3 and the feed roller 2 face each other and contact with each other by the retard pressure N to form a separation nip. The retard roller 3 is biased by a spring (not shown) against the feed roller 2 with a static pressure (N).

The torque limiter 4 does not transmit the rotation of the retard roller shaft 5 in the direction opposite to the sheet conveying direction to the retard roller 3 when the retard roller 3 is loaded with a load larger than a set value. Specifically, the drive transmission force (limit value, set value) of the torque limiter 4 is always set to be larger than the friction force generated between the sheets due to the friction coefficient of the sheets used. Further, the drive transmission force (limit value, set value) of the torque limiter 4 is set to be smaller than the frictional force due to the friction coefficient between the sheet and the feed roller 2. Therefore, when there is only one sheet that enters the separation nip between the feed roller 2 and the retard roller 3 or when there is no sheet, the retard roller 3 rotates together with the feed roller 2. When two or more sheets enter the separation nip, the retard roller 3 rotates in the direction opposite to the sheet conveying direction and separates the sheets one by one.

The retard roller 3 is connected to a retard rotation shaft 6 by gears 9 and 10. The retard rotation shaft 6 is connected to the feed roller shaft 7 by an interlocking gear train 15 and a retard side interlocking gear 13 having a way way mechanism. (Second drive transmission means). As shown in FIG. 2, this second drive transmission means is more than a branch portion between a drive transmission path from the drive motor M of the first drive transmission means to the feed roller 2 and a drive transmission path to the retard roller 3. It is connected to the upstream side (drive motor M side).

Only when the retard roller 3 rotates in the sheet conveying direction, the rotation of the retard roller 3 is transmitted to the retard rotation shaft 6 via the gears 9 and 10, and further, the interlocking gear train 15 is provided by the retard side interlocking gear 13 having a way way mechanism. Be transmitted to. That is, the one-way mechanism of the retard side interlocking gear 13 transmits the rotation to the interlocking gear train 15 when the retard roller 3 rotates in the sheet conveying direction, and when the retard roller 3 rotates in the opposite direction to the sheet conveying direction. The rotation is not transmitted to the interlocking gear train 15.

When the retard roller 3 rotates in the sheet conveying direction, the interlocking gear train 15 transmits the rotational force to the retard reverse drive gear train 14 via the feed roller shaft 7, and the retard roller shaft 5 moves in the opposite direction to the sheet conveying direction. Rotate.

FIG. 3 shows a control block diagram for controlling the sheet feeding apparatus of this embodiment. In FIG. 3, the control unit C stops the drive motor M when the sheet separated by the feed roller 2 and the retard roller 3 reaches the conveying roller (conveying member) 72 arranged on the downstream side in the sheet conveying direction. Take control. A sensor (detection means) d is arranged upstream of the transport roller 72. When the sensor d detects the leading edge of the fed sheet, the control unit C determines that the leading edge of the sheet has reached the conveyance roller 22 based on the detection of the sensor d.

In this configuration, the drive motor M is stopped when the sheet is pulled out from the separation nip by the conveying roller 72 and is conveyed. At this time, the drive from the drive motor M is not transmitted to the retard roller 3. In this situation, the retard roller 3 is in the state of rotating in the sheet conveying direction along with the sheet conveyed by the conveying roller 72, and the retard roller shaft 5 can be rotated in the reverse direction. That is, when the retard roller 3 is rotated by the sheet, the rotation of the retard roller 3 in the sheet conveying direction is transmitted to the retard rotation shaft 6 via the gears 9 and 10, and further, the retard side interlocking having the way way mechanism is performed. It is transmitted to the interlocking gear train 15 by the gear 13.

The drive source gear 16 is equipped with a one-way mechanism (not shown), and even if the drive is transmitted to the interlocking gear train 15, the drive source gear 16 can operate without receiving the load of the drive motor M that is the drive source.

Further, due to the operation of the interlocking gear train 15, the rotational force is also transmitted to the transmission gear 12 that transmits the drive to the pickup roller 1, and the pickup roller 1 rotates in the sheet conveying direction.

The feed roller 2 and the transmission gear 11 are connected by a coupling 20 having a one-way mechanism. Therefore, the rotational force due to the rotation of the feed roller 2 when the sheet is pulled out and conveyed is not transmitted to the feed roller shaft 7 and the transmission gear 12 of the pickup roller 1.

When the peripheral speed of the retard roller 3 is Vc and the transfer speed of the pickup roller 1 rotated by the rotation of the retard roller 3 in the transfer direction is Va, drive transfer is performed so that the relationship of the transfer speeds is Vc>Va. Each gear ratio of the means is set. As a result, when the interlocking gear train 15 is driven, damage to the conveyed sheet due to the sheet conveyance between the pickup roller 1, the feed roller 2 and the retard roller 3 does not occur.

Further, when the interlocking gear train 15 is operating, that is, when the retard roller 3 is rotated together when the drive motor M is stopped, the rotational force is transmitted to the retard roller shaft 5 and the pickup roller 1, so that the drive motor M generates power. It performs the same rotating motion as in the situation where it gets and operates.

The distance from the contact position of the pickup roller 1 with the sheet S to the separation nip where the feed roller 2 and the retard roller 3 face each other is L_ab, from the end position (the leading end position) of the feeding cassette 30 on the downstream side of the sheet S in the transport direction. The distance to the separation nip is L_eb. At this time, the rollers and the cassettes are arranged so that the relationship of the distances is L_ab/Vc≧L_eb/Va.

Further, when the pickup roller 1 and the feed roller 2 are conveying the same sheet, when the feed speed of the feed roller 2 is Vb and the feed speed of the pickup roller 1 is Va, the relation of the above-mentioned feed speeds is Vb≈Va, The gear ratios and rollers of the drive transmission means are set so that

In the above-described conventional reverse rotation drive system and fixed system, when the sheet is fed, the pickup roller 1 and the feed roller 2 receive the power from the drive motor M to rotate, and the downstream roller does not receive the power. There is a situation in which it is rotated by being transported. Under these different circumstances, the conveyance abilities of the pickup roller 1 and the feed roller 2 are different. Even under the conditions of different carrying forces, it is necessary to set the retard pressure N and the torque limiter value (set value of the torque limiter 4) in order to establish the carrying capacity and the separating performance. Here, considering the establishment of separation performance under a certain one of the conveying force conditions, compared to both situations, it is possible to set a retard pressure with a smaller conveying load and a torque limiter value with a smaller component load. , It was not feasible to do performance probabilities under both situations.

For example, in order to improve the separation performance under the condition of rotating with power, the retarding pressure (pressure contact force of the retard roller with respect to the feed roller) is not obtained because of the returning force. The size can be set smaller than in the situation where the sheet is conveyed by the downstream roller and is rotated. However, if the setting is made in this way, in a situation where the sheet is conveyed by the downstream side roller and is rotated by the downstream side roller, the returning force does not work and the retard pressure is smaller, so that the separation performance deteriorates. In this way, if settings are made according to one situation, the performance under the other situation will be impaired, and it will be difficult to improve separation performance (feeding performance) and device durability. It was

On the other hand, in the present embodiment, when the separating operation is required, it is equivalent to the situation in which power is obtained from the drive motor M, so that the range of the separating operation condition can be limited as compared with the conventional method, and the retard pressure and the conveying pressure with a smaller carrying load can be obtained. It is possible to set the torque limiter value with less component load. Therefore, it is possible to improve feeding performance (separation performance) and device durability.

It is possible to provide a sheet feeding device that considers roller wear and component life while stabilizing the sheet separation performance (double feed resistance).

During the operation of the interlocking gear train 15, since the rotational force is transmitted to the retard roller shaft 5 and the pickup roller 1, the same rotational operation is performed under the condition that the drive motor M receives power to operate. Therefore, the range of the separating operation condition can be conventionally limited, and the separating operation condition setting during the sheet passing operation can be distributed to the sheet variety and the component durability.

Further, during the sheet feeding operation, the reverse rotation is always generated, and when the drive motor M is stopped and the sheets other than the sheet pulled out and conveyed to the separation nip are stopped by the retard roller 3, the retard roller 3 is used. Reverse rotation drive does not occur on the roller shaft 5. Therefore, an unnecessary reverse rotation load does not occur on the feeding roller or the separating mechanism component. As a result, it is possible to provide a feeding device that considers roller wear and component life while stabilizing the separation performance (double feed resistance).

[Example 2]
A sheet feeding apparatus according to the second embodiment will be described with reference to FIGS. 4 and 5. Since the schematic configurations of the sheet feeding device and the image forming apparatus are almost the same as those in the above-described embodiment, members having equivalent functions are designated by the same reference numerals, and description thereof will be omitted. In this embodiment, only parts different from the above-described first embodiment will be described.

The retard roller 3 and the retard rotation shaft 6 are connected by gears 9 and 10, and the retard side interlocking gear 13 having a way way transmits the drive to the interlocking gear train 15 only when the retard roller 3 rotates in the sheet conveying direction. (Second drive transmission means). As shown in FIG. 5, this second drive transmission means is connected to a gear provided at one shaft end of the retard roller shaft 5 of the first drive transmission means.

When the retard roller 3 rotates in the sheet conveying direction, the interlocking gear train 15 is connected to the gear provided on the one end of the feed roller shaft 7, and the rotational force is transmitted to the retard reverse rotation drive gear train 14, which causes the retard roller 3 to rotate. The shaft 5 rotates in the direction opposite to the sheet conveying direction.

With this configuration, the retard roller 3 does not receive power from the drive motor, for example, when the sheet is pulled out from the separation nip and conveyed by the conveying force of the conveying roller 72 on the downstream side of the sheet feeding device in the conveying direction. The retard roller shaft 5 can be rotated in the reverse direction when rotating in the transport direction.

The gear 18 of the retard reverse rotation drive gear train 14 of the feed roller shaft 7 has a one-way mechanism and can operate without receiving a load of the drive motor even if the drive is transmitted to the interlocking gear train 15.

The feed roller 2 and the transmission gear 11 are connected by a coupling 20 having a one-way mechanism. Therefore, the rotational force due to the rotation of the feed roller 2 when the sheet is pulled out and conveyed is not transmitted to the feed roller shaft 7 and the transmission gear 12 of the pickup roller 1.

Further, during the operation of the interlocking gear train 15, the rotational force is transmitted to the retard roller shaft 5, but not to the pickup roller 1. Therefore, the separating force (returning force) is higher than that under the condition in which the drive motor M operates with power.

In the present embodiment, when the separating operation is required, the separating force (returning force) is higher than that under the situation in which power is obtained from the drive motor M, so that the separating operation condition can be set so that the separating property is enhanced as compared with the conventional method. Further, it is possible to set the separating operation conditions such as the torque limiter value and the separating pressure for the sheet which needs the separating operation during the feeding operation. Therefore, it is possible to improve feeding performance (separation performance) and device durability.

Further, during the sheet feeding operation, the reverse rotation is always generated, and when the drive motor M is stopped and the sheets other than the sheet pulled out and conveyed to the separation nip are stopped by the retard roller 3, the retard roller 3 is used. Reverse rotation drive does not occur on the roller shaft 5. Therefore, an unnecessary reverse rotation load does not occur on the feeding roller or the separating mechanism component. As a result, it is possible to provide a feeding device that considers roller wear and component life while stabilizing the separation performance (double feed resistance).

[Other Examples]
In the above-described embodiment, the printer is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus may be another image forming apparatus such as a copying machine or a facsimile machine, or another image forming apparatus such as a multi-function machine that combines these functions. The same effect can be obtained by applying the present invention to the sheet feeding device used in these image forming apparatuses.

Further, in the above-described embodiment, the sheet feeding device integrally provided in the image forming apparatus is illustrated, but the present invention is not limited to this. For example, it may be a sheet feeding apparatus that is detachable from the image forming apparatus, and the same effect can be obtained by applying the present invention to the sheet feeding apparatus.

Further, in the above-described embodiment, the sheet feeding device for feeding the sheet such as the recording paper as the recording target is illustrated, but the present invention is not limited to this. For example, the same effect can be obtained even when applied to a sheet feeding device that feeds a sheet such as a document to be read.

Further, in the above-described embodiment, the electrophotographic method is exemplified as the recording method, but the recording method is not limited to this and may be another recording method such as an inkjet method.

C... Control unit M... Drive motor S... Sheet SF... Sheet feeding device d... Sensor 1... Pickup roller 2... Feed roller 3... Retard roller 4... Torque limiter 5... Retard roller shaft 9, 10... Gear 11, 12... Transmission gear 13... Interlocking gear 14... Retarding reverse rotation drive gear train 15... Interlocking gear train 16... Drive source gear 20... Coupling 51A... Printer body 51B... Image forming unit 72... Conveying roller 73... Stacking unit 80... Feed cassette

Claims (7)

A pickup roller that feeds the sheet placed on the placing portion, a feed roller that conveys the sheet fed by the pickup roller, and a retard for facing the feed roller and separating the sheet into one sheet. In a sheet feeding device including a roller,
First drive transmission means for transmitting a driving force from a driving source to rotate the pickup roller and the feed roller in a sheet transport direction and rotate the retard roller in a direction opposite to the sheet transport direction;
A second drive transmission unit that has a one-way mechanism that transmits only the rotation of the retard roller in the sheet transport direction, and that transmits the rotation of the retard roller in the sheet transport direction to the first drive transmission unit;
Equipped with
The first drive transmission means transmits, to the retard roller, a rotation in a direction opposite to a sheet conveying direction of a retard roller shaft to which the retard roller is attached when a load greater than a set value is applied to the retard roller. Has a torque limiter that does not
When the drive source is stopped, the rotation of the retard roller, which rotates along with the sheet conveyed by the conveying member on the downstream side of the feed roller in the sheet conveying direction, in the sheet conveying direction is transmitted through the second drive transmission means. A sheet feeding device, wherein the sheet is fed to a first drive transmission means to rotate the retard roller shaft in a direction opposite to a sheet conveying direction. The first drive transmission unit transmits the rotation of the retard roller in the sheet conveying direction transmitted by the second drive transmission unit to the pickup roller when the drive source is stopped, and the pickup roller conveys the sheet. The sheet feeding device according to claim 1, wherein the sheet feeding device is rotated in a direction. The first drive transmission means has a one-way mechanism that does not transmit the rotation of the retard roller in the sheet conveying direction transmitted by the second drive transmission means to the drive source when the drive source is stopped. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device. When the peripheral speed of the retard roller is Vc and the transfer speed of the pickup roller rotated by the rotation of the retard roller in the sheet transfer direction is Va, the relationship of the transfer speeds is Vc>Va. The sheet feeding device according to any one of claims 1 to 3. The distance from the contact position of the pickup roller with the sheet to the separation nip where the feed roller and the retard roller face each other is L_ab, and the distance from the end position on the downstream side in the sheet conveying direction of the placing section to the separation nip. The sheet feeding device according to claim 4, wherein, when L_eb is L_eb, the distance relationship is L_ab/Vc≧L_eb/Va. When the conveyance speed of the feed roller is Vb and the conveyance speed of the pickup roller is Va while the same sheet is being conveyed by the pickup roller and the feed roller, the relation of the conveyance speeds is Vb≈Va. The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. A sheet feeding device according to any one of claims 1 to 6,
An image forming unit that forms an image on a sheet fed from the sheet feeding device,
An image forming apparatus comprising:

Images