JP6855204B2 - Sheet transfer device and image forming device - Google Patents

Description

The present invention relates to a sheet transporting device for transporting sheets and an image forming apparatus including the same.

Conventionally, in order to improve the loadability on the discharge tray when discharging a sheet, a printer provided with a seating mechanism in the vicinity of a pair of discharge rollers has been proposed (see Patent Document 1). The discharge roller pair of this printer can discharge the sheet to the discharge tray and switch back the sheet by reversing the drive roller in the forward and reverse directions.

The contact portion of the waist mechanism is rotatably supported by the drive shaft of the drive roller via a torque limiter. This contact portion rotates together with the drive shaft and is positioned on the ribs of the printer body during normal rotation and reverse rotation, so that the seat can be seated at a seating position and separated from the seat. Moving. That is, when the sheet is discharged to the discharge tray, the contact portion is located at the sitting position, and when the sheet is switched back, it is located at the separated position. This prevents the occurrence of wrinkles that are likely to occur on the sheet during double-sided transportation.

Japanese Unexamined Patent Publication No. 2006-103869

Here, in general, it is necessary to sufficiently sit down on a sheet having low rigidity such as thin paper, but it is often unnecessary to sit down on a sheet having high rigidity such as thick paper. However, since the waisting mechanism described in Patent Document 1 is always positioned at the same position with respect to the drive roller when the sheet is discharged to the discharge tray, the rigidity of the sheet such as thin paper or thick paper is different. In, do the same amount of sitting.

For this reason, if a low-rigidity seat is seated on a high-rigidity seat in the same way as a low-rigidity seat is seated, the seat will be damaged and the torque for driving the discharge roller pair will increase. There is a risk of chilling.

Further, in order to switch back the seat stably, a sufficient holding pressure is required for the discharge roller pair. For example, when a seating mechanism is provided integrally with the driven rollers of the discharge roller pair, damage to the seat is reduced, but sufficient holding pressure may not be obtained and the seat may not be stably conveyed. ..

Therefore, the present invention provides a sheet transfer device and an image forming device that solve the above-mentioned problems by being configured to achieve both sheet transferability and loadability while suppressing damage to the sheet regardless of the rigidity of the sheet. The purpose is to provide.

The present invention includes a first roller and a second roller forming a nip surface for sandwiching the sheet in the sheet transport device, and transports the sheet in the first transport direction by rotating in the first direction. , The axis of the transport roller pair and the transport roller pair that transport the sheet in the second transport direction opposite to the first transport direction by rotating in the second direction opposite to the first direction. The rotating body is arranged so as to be offset from the transport roller pair in the direction, and is supported so as to be overlapped with the first roller of the transport roller pair in the normal direction of the nip surface, and the rotating body. The second roller is provided with a rotating shaft for supporting, and the second roller is provided with a hollow portion through which the rotating shaft penetrates, and the hollow portion is provided so that the inner diameter portion of the hollow portion and the outer diameter portion of the rotating shaft are separated from each other. The inner diameter of the rotating body is larger than the outer diameter of the rotating shaft, and the rotating body can move independently of the transport roller pair in the normal direction.

According to the present invention, since the rotating body is configured to be movable independently of the transfer roller pair, it is possible to achieve both the transferability and the loadability of the sheet while suppressing damage to the sheet regardless of the rigidity of the sheet. ..

The whole schematic which shows the printer which concerns on 1st Embodiment. The perspective view which shows the discharge unit. Front view explaining that the waist roller overlaps the drive roller. It is a perspective view which shows the waist part, (a) is a perspective view seen from one direction, (b) is a perspective view seen from another direction. The perspective view which shows the hollow part of the driven roller. The schematic diagram which shows the operation of a discharge unit. Front view showing how the seat is seated. A front view showing how a highly rigid seat is seated. The perspective view which shows the discharge unit which concerns on 2nd Embodiment. The schematic diagram which shows the operation of a discharge unit.

<First Embodiment>
〔overall structure〕
First, the first embodiment of the present invention will be described. The printer 1 (image forming apparatus) according to the first embodiment is an electrophotographic laser beam printer that forms a toner image of four colors. As shown in FIG. 1, the printer 1 discharges the loaded sheet to the outside of the machine, the feeding unit 20 for feeding the loaded sheet, the manual feeding unit 15, the image forming unit 10 for forming an image on the sheet, and the sheet. It has a discharge unit 50 (sheet transfer device) and a discharge unit 50 (sheet transfer device). An optional document reading device for reading the image of the document may be provided above the ejection unit 50.

When the image formation command is output to the printer 1, the image formation process by the image forming unit 10 is started based on the image information input from the document reading device or an external computer connected to the printer 1. The image forming unit 10 includes a scanner unit 4 and four process cartridges 10Y, 10M, 10C, and 10Bk that form images of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). , Is equipped. The four process cartridges 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of the images to be formed are different. Only the image forming process of the process cartridge 10Y will be described, and the process cartridges 10M, 10C, and 10Bk will be described. The description is omitted.

The scanner unit 4 irradiates the photosensitive drum 20Y of the process cartridge 10Y with a laser beam based on the input image information. At this time, the photosensitive drum 20Y is precharged by a charging roller (not shown), and an electrostatic latent image is formed on the photosensitive drum 20Y by being irradiated with laser light. After that, the electrostatic latent image is developed by the developing roller 14Y, and a yellow (Y) toner image is formed on the photosensitive drum 20Y.

Similarly, magenta (M), cyan (C) and black (Bk) toner images are formed on the photosensitive drums 20M, 20C and 20Bk of the process cartridges 10M, 10C and 10Bk. The toner images of each color formed on each photosensitive drum are transferred to the intermediate transfer belt 6 by the primary transfer rollers 7Y, 7M, 7C, 7Bk, and transferred to the secondary transfer roller 12 by the intermediate transfer belt 6 rotating in the A direction. Will be done. The intermediate transfer belt 6 is wound around the drive roller 8 and the tension roller 9. The image forming process of each color is performed at the timing of superimposing on the upstream toner image primaryly transferred on the intermediate transfer belt 6.

In parallel with the image forming process described above, the sheet S loaded on the cassette 24 of the feeding unit 20 is fed by the pickup roller 21. The sheets fed by the pickup roller 21 are separated one by one by the feed roller 22 and the separation roller 23, and are conveyed toward the registration roller pair 2. When the sheet is fed from the manual feed feeding unit 15, the sheet is conveyed to the registration roller pair 2 by the pickup roller 16 and the transfer roller pair 33.

The tip of the sheet S conveyed to the registration roller pair 2 is abutted by the registration roller pair 2 which has stopped rotating, and the skew is corrected. Then, the sheet S is conveyed at the timing when the tip of the sheet S is detected by the top sensor 3 arranged downstream in the sheet conveying direction of the registration roller pair 2 and is aligned with the toner image on the intermediate transfer belt 6. Toner.

A full-color toner image on the intermediate transfer belt 6 is transferred to the sheet S by the secondary transfer roller 12. The toner remaining on the intermediate transfer belt 6 after the transfer is collected by the cleaning device 11. Predetermined heat and pressure are applied to the sheet S on which the toner image is transferred by the pressure roller 13a and the heating roller 13b provided on the fixing unit 13, and the toner is melted and fixed. The sheet S that has passed through the fixing unit 13 is discharged by the discharge unit 50 to the discharge tray 25 (support portion) formed on the upper surface of the printer 1.

When an image is formed on both sides of the sheet, the sheet S conveyed to the discharge unit 50 is switched back, and the sheet S is conveyed to the double-sided transfer path 18. The sheet S on the double-sided transfer path 18 is conveyed to the registration roller pair 2 with the front and back and front and back sides of the sheet inverted by the transfer rollers 32 and 33, and the toner image is transferred by the secondary transfer roller 12. ..

[Detailed configuration of discharge unit]
Next, the discharge unit 50, which is a main part of the present invention, will be described in detail. As shown in FIGS. 1 and 2, the discharge unit 50 includes a drive roller portion 35, driven roller portions 44 and 44, a waist portion 36, and a guide member 17. Further, the discharge unit 50 has an upper frame 39a and a lower frame 39b fixed to the printer main body 1A.

The drive roller portion 35 is rotatably supported by the upper frame 39a via a bearing 43, and is fixed to a drive shaft 35b attached to the bearing 43 and a plurality of drive shafts 35b (5 in the present embodiment). It has a drive roller 35a and a drive roller 35a. These drive rollers 35a (one roller) are formed in a crown shape having an axial taper, and are made of, for example, rubber. A drive gear 37 (first gear) connected to a motor M (drive source) capable of forward / reverse rotation is fixed to one end of the drive shaft 35b, and the drive gear 37 is rotated by the motor M. , The drive shaft 35b and the drive roller 35a rotate. The motor M and the drive gear 37 constitute a transmission mechanism 60.

The driven roller portion 44 is located between the holder 38 movably supported by the lower frame 39b, the driven roller 36b rotatably supported by the holder 38 and abutting against the drive roller 35a, and the shaft of the holder 38 and the driven roller 36b. It has a spring 40, which is reduced to. The driven roller 36b is urged to the drive roller 35a by a spring 40 (a urging portion) via the holder 38. The drive roller 35a and the driven roller 36b form a discharge roller pair 34 (conveyor roller pair), and the discharge roller pair 34 has a nip surface N for sandwiching the sheet S. Further, the driven roller portion 44 is arranged symmetrically with respect to the transport center of the sheet S, and the discharge roller pair 34 is also arranged in the same manner. Therefore, the sheet S does not skew due to the pair of these two discharge rollers 34.

The waist portion 36 is rotatably supported by the lower frame 39b via a bearing 42, and is fixed to a rotating shaft 36c attached to the bearing 42 and a plurality of rotating shafts 36c (6 in the present embodiment). It has a bearing roller 36a and. These six waist rollers 36a (rotating bodies) are arranged symmetrically with respect to the transport center of the seat S, and are arranged so as to be offset from the discharge rollers vs. 34 and the drive rollers 35a in the axial direction of the discharge rollers vs. 34. Has been done.

As shown in FIG. 3, the waist roller 36a overlaps the drive roller 35a by a distance X in the normal direction P of the nip surface N. That is, the waist roller 36a is supported so as to be overlapped with the drive roller 35a in the normal direction P of the nip surface N. Further, tapers are provided at both ends of the waist roller 36a in the axial direction in order to suppress damage to the seat.

As shown in FIG. 4A, the lower frame 39b is formed with an elongated hole 39c extending in the normal direction P, and the bearing 42 is movably engaged with the elongated hole 39c in the normal direction P. doing. Specifically, the bearing 42 has a chamfered portion 42a in which both ends in the direction orthogonal to the normal direction P and the axial direction are chamfered, and the chamfered portion 42a is relative to the lateral direction of the elongated hole 39c. They are engaged with a slight gap. Therefore, the bearing 42 and the seating portion 36 are movably supported in the normal direction P while being positioned in the direction orthogonal to the normal direction P and the axial direction.

A spring 41 is stretched between the hook portion 39d of the upper frame 39a and the bearing 42, and the hook portion 39d is opposite to the waist portion 36 with respect to the drive roller portion 35 in the normal direction. It is located on the side. Therefore, the bearing 42 and the seating portion 36 are urged by the urging force of the spring 41 (rotating body urging portion) in the direction approaching the drive roller portion 35 in the normal direction. Then, the bearing 42, as shown in FIG. 4 (b), is positioned by abutting the bearing 4 3. As a result, the amount of overlap of the waist roller 36a of the waist portion 36 with the drive roller 35a in the normal direction P (distance X in FIG. 3) is determined. The spring 41 and the bearings 42, 43 are arranged at both ends of the drive roller portion 35 and the seating portion 36 in the axial direction, respectively.

As shown in FIG. 5, the driven roller 36b (the other roller) has a hollow portion 44a, and the rotating shaft 36c of the seating portion 36 penetrates the hollow portion 44a. The diameter R of the hollow portion 44a, that is, the inner diameter of the driven roller 36b is set to be larger than the outer diameter r of the rotating shaft 36c. The rotating shaft 36c penetrates a substantially central portion of the hollow portion 44a, and a predetermined gap exists between the outer peripheral surface of the rotating shaft 36c and the hollow portion 44a. Therefore, the waist roller 36a fixed to the rotating shaft 36c and the rotating shaft 36c is configured to be movable independently of the driven roller 36b in the normal direction P.

As shown in FIGS. 1 and 6, the guide member 17 is rotatably supported with respect to the printer main body 1A, and has a first guide surface 17a and a second guide surface 17b. The guide member 17 is in contact with the discharge guide 30a whose first guide surface 17a forms a discharge transport path 30 between the fixing unit 13 and the discharge roller pair 34 by its own weight or a spring (not shown).

[Operation of discharge unit]
Next, the operation of the discharge unit 50 will be described. The tip of the sheet S conveyed to the discharge transfer path 30 by the fixing unit 13 first comes into contact with the first guide surface 17a of the guide member 17. Then, the sheet S is conveyed toward the discharge tray 25 by the discharge roller pair 34 that pushes up the guide member 17 and is rotated in the forward direction (first direction) by the motor M. That is, the sheet S is transported in the first transport direction.

When the rear end of the sheet S passes through the guide member 17 when forming an image on both sides of the sheet S, the first guide surface 17a of the guide member 17 comes into contact with the discharge guide 30a again and the motor M reverses, so that the discharge roller pair 34 rotates in the opposite direction (second direction). As a result, the sheet S is switched back and is transported in the second transport direction opposite to the first transport direction.

When the first guide surface 17a of the guide member 17 is in contact with the discharge guide 30a, the reversing guide 31a forming the reversing transport path 31 for guiding the sheet S on the double-sided transport path 18 and the second guide surface 17b of the guide member 17 And are connected smoothly. As a result, the sheet S that is switched back and transported in the second transport direction is guided to the reverse transport path 31 by the second guide surface 17b of the guide member 17 and the reverse guide 31a.

When the sheet S is conveyed by the discharge roller pair 34, the sheet S is seated. Specifically, as shown in FIG. 7, the seat S is wavyly habituated by the drive roller 35a, the driven roller 36b, and the waist roller 36a arranged alternately with the drive roller 35a in the axial direction. At this time, the waist roller 36a moves a predetermined distance in the normal direction away from the drive roller 35a against the urging force of the spring 41 due to the stiffness of the seat S.

When the sheet S to be conveyed is a sheet having relatively low rigidity such as plain paper or thin paper, the moving distance of the waist roller 36a is small, and as shown in FIG. 7, the waist roller 36a is driven in the normal direction. It overlaps the roller 35a sufficiently. As a result, the downward sagging is reduced especially when a sheet having relatively low rigidity such as plain paper or thin paper is discharged to the discharge tray 25. Therefore, the loadability of the sheet S on the discharge tray 25 can be improved.

On the other hand, when the sheet S to be conveyed is a sheet having a relatively high rigidity such as thick paper, the moving distance of the waist roller 36a is large, and as shown in FIG. 8, the waist roller 36a is a drive roller in the normal direction. There is almost no overlap with 35a. Therefore, the discharge unit 50 does not sit on a highly rigid seat that does not need to be seated in the first place, suppresses damage to the seat S by the seating roller 36a, and drives the discharge roller vs. 34. Can be reduced.

Further, since the waist roller 36a can move independently of the driven roller 36b in the normal direction, even if the waist roller 36a moves according to the rigidity of the seat S, the driving roller 35a and the driven roller 36b will be used. The holding pressure of the sheet S is kept constant. From the above, regardless of the rigidity of the seat S, it is possible to achieve both the transportability and the loadability of the seat while suppressing damage to the seat S.

<Second embodiment>
Next, a second embodiment of the present invention will be described. The second embodiment is configured so that the drive is input from the motor M to the waist portion 36 of the first embodiment. is there. Therefore, the same configuration as that of the first embodiment will be described by omitting the illustration or adding the same reference numerals to the drawings.

As shown in FIG. 9, a roller gear 45 (second gear) that meshes with the drive gear 37 is attached to one end of the rotary shaft 36c of the discharge unit 150 (seat transfer device) according to the second embodiment. ing. The motor M, the drive gear 37, and the roller gear 45 constitute a transmission mechanism 160.

The drive gear 37 and the roller gear 45 have large modules set so as to maintain the meshed state within the moving range of the waist roller 36a that moves together with the roller gear 45. For example, the module is set to 1.25. Further, the number of teeth of the drive gear 37 and the roller gear 45 is set to a value such that the peripheral speeds of the drive roller 35a and the waist roller 36a are substantially uniform.

In the present embodiment, when the motor M rotates and the drive roller 35a rotates, the driving force is transmitted to the waist portion 36 via the drive gear 37 and the roller gear 45, and the waist roller 36a also rotates. Then, even if a sheet having a relatively high rigidity such as thick paper is conveyed and the waist portion 36 is largely retracted in the normal direction, the modules of the drive gear 37 and the roller gear 45 are set large, so that the waist roller The rotation of 36a does not stop.

Then, for example, as shown in FIG. 10, when the discharge roller pair 34 is rotating in the positive direction, the waist roller 36a is rotating in the arrow W direction (counterclockwise). Here, the waist roller 36a has a larger outer diameter than the driven roller 36b and is arranged substantially coaxially with the driven roller 36b. Therefore, even when the sheet S leans against the waist roller 36a under conditions such as curled thin paper where it is difficult to obtain a sufficient waist effect, the sheet S is moved in the arrow Y direction by the waist roller 36a. Is pushed out to. As a result, the sheet S falls on the discharge tray 25, and the loadability of the sheet S can be improved.

In the first and second embodiments described above, the waist roller 36a is arranged on the driven roller 36b side, but the waist roller 36a may be arranged on the drive roller 35a side.

Further, in the first and second embodiments described above, the driven roller 36b is formed in a hollow shape, and the rotating shaft 36c of the waist roller 36a is passed through the hollow portion 44a of the driven roller 36b. Not limited to. For example, the waist roller may be configured to have a hollow shape, and the hollow portion of the waist roller may be configured to penetrate the rotation shaft of the driven roller.

Further, in the first and second embodiments described above, the waist roller 36a is configured to be movable in the normal direction of the nip surface N, but the present invention is not limited to this. That is, the waist roller 36a may be configured to be movable in a direction intersecting the nip surface N, in other words, may be configured to be movable in a direction having a normal direction component. Further, the waist roller 36a is not limited to a cylindrical shape, and may have another shape such as an elliptical cross section.

Further, in the first and second embodiments described above, the discharge roller pair 34 is configured to rotate in the forward direction or the reverse direction by rotating the motor M in the forward and reverse directions, but the present invention is not limited to this. For example, the motor M may rotate in only one direction, and a mechanism capable of reversing the rotation direction of the driving force from the motor M may be provided in the drive transmission path between the motor M and the discharge roller pair 34.

Further, in the first and second embodiments described above, the configuration in which the driving force of the motor M is transmitted by gears is used, but the driving force of the motor M can be transmitted not only by gears but also by, for example, a belt and a pulley. It may be configured as.

Further, the ejection unit in the first and second embodiments described above may be arranged not only for ejecting the sheet to the outside of the machine but also at another place in the printer 1 and used as a sheet conveying device.

Moreover, although the description has been made using the electrophotographic printer 1 in any of the above-described forms, the present invention is not limited to this. For example, the present invention can be applied to an inkjet image forming apparatus that forms an image on a sheet by ejecting an ink liquid from a nozzle.

1: Image forming device (printer) / 10: Image forming part / 25: Support part (discharge tray) / 34: Transfer roller pair (discharge roller pair) / 35a: One roller (drive roller) / 36a: Rotating body ( Waist roller) / 36b: The other roller (driven roller) / 36c: Rotating shaft / 37: First gear (drive gear) / 40: Biasing part (spring) / 41: Rotating body urging part (spring) / 44a: Hollow part / 45: Second gear (roller gear) / 50, 150: Seat transfer device (discharge unit) / 60, 160: Transmission mechanism / M: Drive source (motor) / N: Nip surface / P: Normal direction / r: Outer diameter / R: Diameter / S: Sheet

Claims (11)

A first roller and a second roller forming a nip surface for sandwiching the sheet are included, and the sheet is conveyed in the first conveying direction by rotating in the first direction, which is opposite to the first conveying direction. A pair of transport rollers that transport the sheet in the second transport direction opposite to the first transport direction by rotating in the second direction of the above.
A rotating body that is arranged so as to be offset from the transport roller pair in the axial direction of the transport roller pair and is supported so as to be overlapped with the first roller of the transport roller pair in the normal direction of the nip surface. When,
A rotating shaft for supporting the rotating body , and
The second roller includes a hollow portion through which the rotating shaft penetrates, and the inner diameter of the hollow portion is the outer diameter of the rotating shaft so that the inner diameter portion of the hollow portion and the outer diameter portion of the rotating shaft are separated from each other. Greater than
The rotating body can move independently of the transport roller pair in the normal direction.
A sheet transfer device characterized by this. The drive source that drives the first roller and
An urging portion for urging the second roller of the transport roller pair to the first roller is provided.
The sheet transport device according to claim 1. A rotating body urging portion for urging the rotating body in a direction approaching the first roller in the normal direction is provided.
The sheet transport device according to claim 2, wherein the sheet transport device is characterized by this. A holder that rotatably supports the second roller is provided.
The urging portion urges the holder.
The sheet transport device according to claim 2 or 3, wherein the sheet transport device is characterized by the above. The support portion of the holder that supports the second roller is located outside the hollow portion in a direction orthogonal to the axial direction of the rotation axis.
The sheet transport device according to claim 4, wherein the sheet transport device is characterized by this. A transmission mechanism for driving and transmitting the driving force of the driving source to the first roller and the rotating body is provided.
The sheet transport device according to any one of claims 2 to 5, wherein the sheet transport device is characterized by this. The transmission mechanism can transmit the driving force to the rotating body by engaging with the first gear to which the driving force from the driving source is input and can transmit the driving force to the first roller and the first gear. Has a second gear,
The first gear and the second gear maintain the meshed state within the moving range of the rotating body.
The sheet transport device according to claim 6, wherein the sheet transport device is characterized by this. Equipped with a support to support the ejected sheet,
The transport roller pair rotates in the first direction to discharge the sheet to the support portion.
The sheet transport device according to any one of claims 1 to 7, wherein the sheet transport device is characterized by this. A first bearing for supporting the rotating shaft is provided.
The first bearing can move along the normal direction by engaging with a hole extending in the normal direction.
The sheet transport device according to any one of claims 1 to 8, wherein the sheet transport device is characterized by this. A drive shaft that supports the first roller and
A second bearing that supports the drive shaft is provided.
When the rotating body moves in the direction approaching the first roller in the normal direction, the first bearing comes into contact with the second bearing, so that the first bearing is positioned.
The sheet transport device according to claim 9. An image forming part that forms an image on the sheet,
The sheet transport device according to any one of claims 1 to 10 is provided.
An image forming apparatus characterized in that.

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