Patent Application
20230322512
The present invention relates to a sheet conveyance apparatus that conveys a sheet and an image forming apparatus including the same.
In the related art, there has been proposed an image forming apparatus that corrects a skew of a sheet by forming a loop on the sheet by abutting a leading edge of the sheet conveyed by a pre-registration roller pair against a nip portion of a registration roller pair that is stopping rotation (see JP 2017-190198 A). The image forming apparatus includes a separating unit for separating the pre-registration roller pair from each other.
The sheet subjected to the skew correction is conveyed toward the secondary transfer portion by the pre-registration roller pair, and at this time, a force for returning the skew is generated in the sheet by the loop reaction force. Therefore, the image forming apparatus reduces the loop pressure generated in the sheet by separating (releasing) the nip portion of the pre-registration roller pair.
However, the image forming apparatus described in JP 2017-190198 A causes the pre-registration roller pair to abut on each other again after releasing the nip portion of the pre-registration roller pair. At this time, the orientation of the sheet may not be stable, and conveyance failure such as slip may occur in the pre-registration roller pair.
According to a first aspect of the present invention, a sheet conveyance apparatus includes a conveyance rotating member pair configured to convey a sheet in a sheet conveyance direction, a skew correction portion including a first abutment portion against which a leading edge of the sheet conveyed by the conveyance rotating member pair abuts, and a second abutment portion that is disposed at a position different from the first abutment portion in a width direction orthogonal to the sheet conveyance direction and corrects a skew of the sheet in a case where the leading edge of the sheet abuts against the second abutment portion together with the first abutment portion, and a guide portion that guides the sheet conveyed by the conveyance rotating member pair toward the first abutment portion and the second abutment portion. The guide portion includes a guide surface that is disposed between the first abutment portion and the second abutment portion in the width direction and forms a conveyance path through which a sheet passes, a first recess portion that is disposed upstream of the first abutment portion in the sheet conveyance direction, is disposed at a position overlapping with the first abutment portion in the width direction, and is recessed to an opposite side to the conveyance path with respect to the guide surface, and a second recess portion that is disposed upstream of the second abutment portion in the sheet conveyance direction, is disposed at a position overlapping with the second abutment portion in the width direction, and is recessed to an opposite side to the conveyance path with respect to the guide surface.
According to a second aspect of the present invention, a sheet conveyance apparatus includes a conveyance rotating member pair configured to convey a sheet in a sheet conveyance direction, a skew correction portion including a first rotating member pair having a first nip against which a leading edge of the sheet conveyed by the conveyance rotating member pair abuts, and a second rotating member pair disposed at a position different from the first rotating member pair in a width direction orthogonal to the sheet conveyance direction and having a second nip that corrects a skew of the sheet in a case where the leading edge of the sheet abuts against the second nip together with the first nip, and a guide portion that guides the sheet conveyed by the conveyance rotating member pair toward the first nip and the second nip. The guide portion includes a guide surface that forms a conveyance path through which a sheet passes, and a recess portion that is disposed upstream of the first nip and the second nip in the sheet conveyance direction and between the first nip and the second nip in the width direction, and is recessed to an opposite side to the conveyance path with respect to the guide surface.
According to a third aspect of the present invention, a sheet conveyance apparatus includes a conveyance rotating member pair configured to convey a sheet in a sheet conveyance direction, a skew correction portion including an abutment portion that corrects a skew of a sheet in a case where a leading edge of the sheet conveyed by the conveyance rotating member pair abuts against the skew correction portion, and a guide portion that guides the sheet conveyed by the conveyance rotating member pair toward the abutment portion. The guide portion includes a first guide surface that is disposed on a first side with respect to the abutment portion in a width direction orthogonal to the sheet conveyance direction and forms a conveyance path through which the sheet passes, a second guide surface that is disposed on a second side with respect to the abutment portion in the width direction and forms the conveyance path, and a recess portion that is disposed upstream of the abutment portion in the sheet conveyance direction, is disposed at a position overlapping with the abutment portion in the width direction, and is recessed to an opposite side to the conveyance path with respect to the first guide surface and the second guide surface.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
First, a first embodiment of the present invention will be described. A printer 1 as an image forming apparatus is an electrophotographic laser beam printer that forms a monochrome toner image. In the following description, a sheet S is a sheet on which an image is formed by the printer 1, and includes, for example, paper, an overhead transparency (OHT) sheet, and the like.
As illustrated in
When an image forming job is output to the printer 1, the image forming process by the image forming unit 60 is started on the basis of image information input from an external computer or the like connected to the printer 1. The image forming unit 60 as an image forming unit includes a laser scanner 62, a process cartridge P having a photosensitive drum 61, and a transfer roller 631. A charging roller, a developing roller, and the like (not illustrated) are provided around the photosensitive drum 61. The photosensitive drum 61 and the transfer roller 631 form a transfer nip T1.
The laser scanner 62 irradiates the photosensitive drum 61 with laser light on the basis of the input image information. At this time, the photosensitive drum 61 is charged in advance by a charging roller, and an electrostatic latent image is formed on the photosensitive drum 61 by being irradiated with laser light. Thereafter, the electrostatic latent image is developed by the developing roller, and a monochrome toner image is formed on the photosensitive drum 61.
In parallel with the above-described image forming process, the sheet S is fed from the feeding unit 30. The feeding unit 30 includes a cassette 2 that can be pulled out and attached to an apparatus body 1A of the printer 1, a feeding roller 31, and a separation roller pair 32. The sheet S stored in the cassette 2 is fed by a feeding roller 31, and the sheet S fed by the feeding roller 31 is separated one by one by the separation roller pair 32.
Note that the cassette 2 may be provided with an intermediate plate that can support and lift a sheet, and for example, the intermediate plate may be raised by receiving an image forming job, and the sheet supported by the intermediate plate and the feeding roller may be brought into contact with each other. In the separation roller pair 32, one of the roller pair may be a pad or the like, and a torque limiter method, a retard roller method, or the like can be applied.
The toner image on the photosensitive drum 61 is transferred to the sheet S fed from the feeding unit 30 and conveyed by the sheet conveyance apparatus 90 at the transfer nip T1 by the electrostatic load bias applied to the transfer roller 631. The remaining toner remaining on the photosensitive drum 61 is collected by a cleaning blade (not illustrated). Predetermined heat and pressure are applied to the sheet S to which the toner image has been transferred by a fixing film 71 and a pressure roller 72 of the fixing device 7, and the toner is melted and fixed. A heating member such as a ceramic heater is disposed inside of the fixing film 71. The sheet S having passed through the fixing device 7 is discharged to the discharge tray 9 by the discharge roller pair 8.
When images are formed on both surfaces of the sheet S, the sheet S on which the images are formed on the first surface is switched back by a reverse conveyance roller pair 35 and conveyed to a duplex conveyance path CP2. The sheet S conveyed through the duplex conveyance path CP2 is conveyed again to the transfer nip T1 by the sheet conveyance apparatus 90, and an image is formed on the second surface at the transfer nip T1 and discharged to the discharge tray 9.
Next, the sheet conveyance apparatus 90 will be described with reference to
As illustrated in
In the present embodiment, five registration roller pairs 51 are arranged side by side in the width direction W orthogonal to a sheet conveyance direction CD. The registration roller pair 51 as a rotating member pair includes a registration roller 511 and a registration driven roller 512. The registration roller 511 and the registration driven roller 512 form a conveyance nip N1 (see
Next, the skew correction unit 53 will be described with reference to
Further, the registration frame 52 has a plurality of guide surfaces 52a which are provided to be spaced apart from each other in the width direction W and form the conveyance path CP1, and the skew correction member 531 and the registration driven roller 512 are arranged in the gaps between the guide surfaces 52a. Therefore, the guide surface 52a is disposed between the skew correction member 531 and the registration driven roller 512. The guide surfaces 52a are disposed so as to overlap each other when viewed in the width direction W.
The skew correction unit 53 is swingably supported with respect to the registration frame 52 about a swing shaft 53P, and is positioned at a standby position illustrated in
The sheet contact surface 531a protrudes to the conveyance path CP1 when the skew correction member 531 is located at the contact position, and is disposed upstream of the conveyance nip N1 of the registration roller pair 51 in the sheet conveyance direction CD. At this time, the sheet contact surface 531a serving as an inclined surface is inclined upstream in the sheet conveyance direction CD toward the leading edge of the sheet contact surface, that is, away from the main body portion 531b when viewed in the width direction W. In other words, the sheet contact surface 531a is inclined so as to approach a recess portion 52b described below in the thickness direction of the sheet as the sheet contact surface 531a extends downstream in the sheet conveyance direction CD when viewed in the width direction. When viewed in the width direction W, a leading edge 531c of the sheet contact surface 531a is located more inward of the opposing guide 54 than the opposing guide surface 54a, and the root portion 531d of the sheet contact surface 531a is located inside of the registration frame 52 with respect to the guide surface 52a. The opposing guide surface 54a of the opposing guide 54, serving as the opposing guide portion, and the guide surface 52a form a part of the conveyance path CP1.
More specifically, in the registration frame 52, a recess portion 52b is formed at a position overlapping each skew correction member 531 in the width direction W, and the recess portion 52b is recessed to an opposite side to the conveyance path CP1 with respect to the guide surface 52a. A root portion 531d of the sheet contact surface 531a enters the inside of the recess portion 52b. The recess portion 52b at least extends upstream from a position overlapping with the root portion 531d of the sheet contact surface 531a in the sheet conveyance direction CD, but may also extend downstream from a position overlapping with the root portion 531d. Note that the recess portion 52b may have any configuration such as a hole, an opening, and a groove as long as the recess portion is formed such that the space communicates with the inside of the registration frame 52 more than the guide surface 52a when viewed in the width direction W.
In addition, among the sheet contact surfaces 531a of the plurality of skew correction members 531, the sheet contact surface arranged outer side of the conveyance path CP1 in the width direction W is located closer to the upstream in the sheet conveyance direction CD than the sheet contact surface arranged inner side of the conveyance path CP1. In the present embodiment, since the four skew correction members 531 are provided, the two sheet contact surfaces 531a arranged on the outer side in the width direction W are referred to as a third abutment portion and a fourth abutment portion. At this time, the third abutment portion and the fourth abutment portion are located upstream of the two sheet contact surfaces 531a as the first abutment portion and the second abutment portion disposed inside in the width direction W in the sheet conveyance direction CD.
Next, the operation of the skew correction unit 53 will be described with reference to
At this time, when the sheet S is conveyed in a skewed state, the leading edge of the sheet S on the leading side in the width direction W first comes into contact with the sheet contact surface 531a. Then, the sheet S turns about the contact portion with the sheet contact surface 531a that abuts first, and also abuts on the sheet contact surface 531a of the other skew correction member 531.
As illustrated in
As described above, the recess portion 52b is formed at a position overlapping with the skew correction member 531 of the registration frame 52 in the width direction W. Therefore, the leading edge Sa of the sheet S whose skew has been corrected has a region abutting on the guide surface 52a and a region entering the recess portion 52b, and these regions are different in position from each other in the thickness direction of the sheet.
For example, when the two sheet contact surfaces 531a and 531a on the center side in the width direction W are defined as a first abutment portion and a second abutment portion, the skew of the sheet S is corrected by the leading edge Sa abutting against the first abutment portion and the second abutment portion. Then, the leading edge Sa of the sheet S is sandwiched between the guide surface 52a disposed between the sheet contact surfaces 531a and 531a in the width direction W and the sheet contact surfaces 531a and 531a, and the leading edge Sa of the sheet S becomes into a wavy shape. The leading edge Sa enters the recess portions 52b and 52b serving as a first recess portion and a second recess portion located at positions overlapping with the sheet contact surfaces 531a and 531a in the width direction W, respectively.
For example, when one of the two sheet contact surfaces 531a and 531a on the center side in the width direction W is set as an abutment portion, if the abutment portion is sufficiently long in the width direction W, the skew of the sheet S is corrected only by the abutment portion. The leading edge Sa of the sheet S is sandwiched between the recess portion 52b located at a position overlapping with the sheet contact surface 531a, which is the abutment portion, in the width direction W and the guide surfaces 52a and 52a, which are the first guide surface and the second guide surface, disposed on one side and the other side of the recess portion 52b or the abutment portion in the width direction W. The leading edge Sa of the sheet S enters the recess portion 52b and becomes into a wavy shape.
As described above, the leading edge Sa of the sheet S is sandwiched between the guide surface 52a displaced in the width direction W and the thickness direction of the sheet and the sheet contact surface 531a, so that the leading edge Sa of the sheet S has a wavy shape. As described above, since the sheet contact surface 531a of the skew correction member 531 is located on the upstream in the sheet conveyance direction CD as the sheet contact surface is disposed on the outer side of the conveyance path CP1 in the width direction W, the sheet contact surface 531a is easily sandwiched between the guide surface 52a and the sheet contact surface 531a up to the edge of the sheet. Therefore, the entire sheet can be easily waved.
Further, since the sheet S is conveyed by the conveyance unit 4 even while the movement of the sheet S in the sheet conveyance direction CD is restricted by the sheet contact surface 531a, a loop is formed upstream of the leading edge Sa in the sheet conveyance direction CD. In the related art, the loop formed on the sheet S abuts on the conveyance guide (for example, the registration frame 52), and the leading edge Sa of the sheet S pushes up the skew correction unit 53 using the reaction force.
However, the size of the loop formed on the sheet S is larger on the side that first abuts on the sheet contact surface 531a than on the side that last abuts on the sheet contact surface in the width direction W. Since the size of the loop formed on the sheet S in the width direction W is different, the reaction force received by the sheet S from the conveyance guide is different in the width direction W. For this reason, a phenomenon (hereinafter, referred to as skew returning) in which the skew of the sheet S gradually returns due to a difference in reaction force received in the width direction W after the skew correction unit 53 is pushed up occurs.
However, in the present embodiment, as described above, the cross section secondary moment of the sheet S is increased by waving the leading edge Sa of the sheet S, and the rigidity is temporarily improved. Therefore, even if the leading edge Sa is conveyed by the conveyance unit 4 in a state where the leading edge Sa is dammed by the sheet contact surface 531a, it is difficult to form a loop on the sheet S. Therefore, as illustrated in
When the skew correction unit 53 rotates about the swing shaft 53P from the standby position, the sheet contact surface 531a retreats from the conveyance path CP1, and the sheet S can pass through the conveyance path CP1. As a result, the sheet S passes through the registration unit 5 and is conveyed downstream in the sheet conveyance direction CD. While the sheet S is passing through the registration unit 5, the skew correction member 531 is biased by the tension spring 535 and rubs against the surface of the sheet S. When a trailing edge of the sheet S passes through the skew correction member 531, the skew correction member 531 returns to the standby position by the tension spring 535.
As described above, in the present embodiment, by waving the leading edge Sa of the sheet S, the rigidity of the sheet S itself can be temporarily improved, and the loop formed on the sheet S at the time of skew correction can be reduced. As a result, the skew returning can be reduced, and the conveyance failure such as the skew of the sheet can be reduced. In addition, the print image accuracy can be improved, and a good product can be obtained. In particular, for example, a sheet having a small grammage such as thin paper tends to have a large loop formed at the time of the skew correction, but according to the present embodiment, the skew can be satisfactorily corrected regardless of the grammage of the sheet. Furthermore, since the present embodiment has a simple configuration, the skew of the sheet can be corrected with an inexpensive configuration.
Next, a modification of the first embodiment will be described with reference to
In the first embodiment, the plurality of registration rollers 512 are independently swingably held by the registration holder 513. As illustrated in
The skew correction unit 57 as the skew correction portion includes a plurality of (four in the present embodiment) skew correction members 571 arranged side by side in the width direction W, and a connecting member 572 connecting the skew correction members 571. The skew correction unit 57 is supported so as to be rotatable about the registration driven roller shaft 514. The skew correction unit 57 is biased to the standby position by a torsion coil spring 575. Note that the skew correction unit 57 may be rotatably supported by the rotation shaft of either one roller, serving as one rotating member, of the registration roller pair 51, and may be rotatably supported by the rotation shaft of the registration driven roller 512.
The operation of the skew correction unit 57 is similar to that of the skew correction unit 53 of the first embodiment. As illustrated in
At this time, when the sheet S is conveyed in a skewed state, the leading edge of the sheet S on the leading side in the width direction W first comes into contact with the sheet contact surface 571a. Then, the sheet S turns about the contact portion with the sheet contact surface 571a that abuts first, and also abuts on the sheet contact surface 571a of the other skew correction member 571.
As illustrated in
As described above, the recess portion 52b is formed at a position overlapping with the skew correction member 571 of the registration frame 52 in the width direction W. Therefore, the leading edge Sa of the sheet S whose skew has been corrected has a region abutting on the guide surface 52a and a region entering the recess portion 52b, and these regions are different in position from each other in the thickness direction of the sheet.
By waving the leading edge Sa of the sheet S, the cross section secondary moment of the sheet S is increased, and the rigidity is temporarily improved. Therefore, even if the leading edge Sa is conveyed by the conveyance unit 4 in a state where the leading edge Sa is dammed by the sheet contact surface 571a, it is difficult to form a loop on the sheet S. Therefore, as illustrated in
When the skew correction unit 57 rotates about the registration driven roller shaft 514 from the standby position, the sheet contact surface 571a retreats from the conveyance path CP1, and the sheet S can pass through the conveyance path CP1. As a result, the sheet S passes through the registration unit 5A and is conveyed downstream in the sheet conveyance direction CD. While the sheet S is passing through the registration unit 5A, the skew correction member 571 is biased by the torsion coil spring 575 and rubs against the surface of the sheet S. When the trailing edge of the sheet S passes through the skew correction member 571, the skew correction member 571 returns to the standby position by the torsion coil spring 575.
As described above, in the present embodiment, by waving the leading edge Sa of the sheet S, the rigidity of the sheet S itself can be temporarily improved, and the loop formed on the sheet S at the time of skew correction can be reduced. As a result, the skew returning can be reduced, and the conveyance failure such as the skew of the sheet can be reduced. In addition, the print image accuracy can be improved, and a good product can be obtained. In particular, for example, a sheet having a small grammage such as thin paper tends to have a large loop formed at the time of the skew correction, but according to the present embodiment, the skew can be satisfactorily corrected regardless of the grammage of the sheet. Furthermore, since the present embodiment has a simple configuration, the skew of the sheet can be corrected with an inexpensive configuration.
Next, a second embodiment of the present invention will be described, but the second embodiment is different from the first embodiment in the pressurization configuration of the registration driven roller and the configuration of the skew correction unit. Therefore, a configuration similar to that of the first embodiment will be described by omitting illustration or attaching the same reference numerals to the drawings.
As illustrated in
A registration holder 1013 is supported as linearly movable by the registration frame 52, and the registration holder 1013 rotatably supports a plurality of (five in the present embodiment) registration rollers 512. The registration driven roller 512 is pressed against the registration roller 511 by a spring (not illustrated) that biases the registration holder 1013.
Next, the skew correction unit 103 will be described with reference to
In addition, the registration frame 52 has a plurality of guide surfaces 52a provided with gaps therebetween in the width direction W, and the skew correction member 1031 and the registration driven roller 512 are arranged in the gaps between the guide surfaces 52a. Therefore, the guide surface 52a is disposed between the skew correction member 1031 and the registration driven roller 512.
The skew correction unit 103 is rotatably supported with respect to the registration frame 52 about the shaft member 1032, and is positioned at the standby position illustrated in
The sheet contact surface 1031a protrudes to the conveyance path CP1 when the skew correction member 1031 is located at the contact position, and is disposed upstream of the conveyance nip N1 of the registration roller pair 51 in the sheet conveyance direction CD. At this time, the sheet contact surface 1031a as the abutment portion, the first abutment portion, and the second abutment portion is inclined upstream in the sheet conveyance direction CD toward the leading edge of the sheet contact surface, that is, away from the main body portion 1031b when viewed in the width direction W. When viewed in the width direction W, a leading edge 1031c of the sheet contact surface 1031a is located inside of the opposing guide 54, and the root portion 531d of the sheet contact surface 1031a is located inside of the registration frame 52 with respect to the guide surface 52a.
As described above, the recess portion 52b is formed at a position overlapping with the skew correction member 1031 of the registration frame 52 in the width direction W. The recess portion 52b at least extends upstream from a position overlapping with the root portion 1031d of the sheet contact surface 1031a in the sheet conveyance direction CD, but may also extend downstream from a position overlapping with the root portion 531d. Note that the recess portion 52b may have any configuration such as a hole, an opening, and a groove as long as the recess portion is formed such that the space communicates with the inside of the registration frame 52 more than the guide surface 52a when viewed in the width direction W.
In addition, among the sheet contact surfaces 1031a of the plurality of skew correction members 1031, the sheet contact surface arranged outer side of the conveyance path CP1 in the width direction W is located closer to the upstream in the sheet conveyance direction CD than the sheet contact surface arranged inner side of the conveyance path CP1. In the present embodiment, since the four skew correction members 1031 are provided, the two sheet contact surfaces 1031a arranged on the outer side in the width direction W are located upstream of the two sheet contact surfaces 1031a arranged on the inner side in the sheet conveyance direction CD.
Next, the operation of the skew correction unit 103 will be described with reference to
At this time, when the sheet S is conveyed in a skewed state, the leading edge of the sheet S on the leading side in the width direction W first comes into contact with the sheet contact surface 1031a. Then, the sheet S turns about the contact portion with the sheet contact surface 1031a that abuts first, and also abuts on the sheet contact surface 1031a of the other skew correction member 1031.
As illustrated in
As described above, the recess portion 52b is formed at a position overlapping with the skew correction member 1031 of the registration frame 52 in the width direction W. Therefore, the leading edge Sa of the sheet S whose skew has been corrected has a region abutting on the guide surface 52a and a region entering the recess portion 52b, and these regions are different in position from each other in the thickness direction of the sheet.
Further, since the sheet S is conveyed by the conveyance unit 4 even while the movement of the sheet S in the sheet conveyance direction CD is restricted by the sheet contact surface 1031a, a loop is formed upstream of the leading edge Sa in the sheet conveyance direction CD. However, by waving the leading edge Sa of the sheet S, the cross section secondary moment of the sheet S is increased, and the rigidity is temporarily improved. Therefore, even if the leading edge Sa is conveyed by the conveyance unit 4 in a state where the leading edge Sa is dammed by the sheet contact surface 1031a, it is difficult to form a loop on the sheet S. Therefore, as illustrated in
When the skew correction unit 103 rotates about the shaft member 1032 from the standby position, the sheet contact surface 1031a retreats from the conveyance path CP1, and the sheet S can pass through the conveyance path CP1. As a result, the sheet S passes through the registration unit 10 and is conveyed downstream in the sheet conveyance direction CD. While the sheet S is passing through the registration unit 10, the skew correction member 1031 rubs against the surface of the sheet S by the biasing force of the compression spring 703. When the trailing edge of the sheet S passes through the skew correction member 1031, the skew correction member 1031 shifts to the next standby position.
As described above, in the present embodiment, by waving the leading edge Sa of the sheet S, the rigidity of the sheet S itself can be temporarily improved, and the loop formed on the sheet S at the time of skew correction can be reduced. As a result, the skew returning can be reduced, and the conveyance failure such as the skew of the sheet can be reduced. In addition, the print image accuracy can be improved, and a good product can be obtained. In particular, for example, a sheet having a small grammage such as thin paper tends to have a large loop formed at the time of the skew correction, but according to the present embodiment, the skew can be satisfactorily corrected regardless of the grammage of the sheet.
Furthermore, since the present embodiment has a simple configuration, the skew of the sheet can be corrected with an inexpensive configuration. Further, the skew correction unit 103 rotates only in one direction by being pressed by the leading edge Sa of the sheet S. Therefore, when the trailing edge of the sheet S passes through the first sheet contact surface 1031a, the second sheet contact surface 1031a immediately protrudes to the conveyance path CP1, and the skew correction of the succeeding sheet can be prepared. Therefore, it is possible to reduce the interval between sheets conveyed continuously, that is, the sheet interval, and to improve the throughput.
Next, a third embodiment of the present invention will be described, but the third embodiment is different from the first embodiment in the pressurizing configuration of the registration roller and the configuration of the skew correction unit. Therefore, a configuration similar to that of the first embodiment will be described by omitting illustration or attaching the same reference numerals to the drawings.
As illustrated in
One registration driven roller shaft 514 is supported by the registration frame 52, and a plurality of (five in the present modification) registration rollers 512 are rotatably supported by the registration driven roller shaft 514. The registration driven roller shaft 514 is biased toward the registration roller 511 by a biasing member (not illustrated).
In the present embodiment, the skew correction member against which the leading edge Sa of the sheet S abuts is not provided, and the skew of the sheet S is corrected by the leading edge Sa abutting the conveyance nip N1. That is, in the present embodiment, a stop roller system is adopted. The drive control of the registration roller 511 is performed by the control unit 95 (see
The registration frame 52 is provided with gaps therebetween in the width direction W, and includes a plurality of guide surfaces 52a forming the conveyance path CP1. The recess portion 52b and the registration driven roller 512 similar to those in the first and second embodiments are arranged in these gaps. Therefore, the guide surface 52a is disposed between the recess portion 52b and the registration driven roller 512, and the recess portion 52b is disposed between the two adjacent registration rollers 512.
On the registration frame 52, a swing guide 114 is swingably supported about a swing shaft 114c extending in the width direction W, and the swing guide 114 is positioned at the standby position illustrated in
In the present embodiment, the four protrusion portions 114a are formed in one swing guide 114, and the four protrusion portions 114a swing integrally, but the present invention is not limited thereto. For example, a plurality of swing guides that swing separately may be provided, and each swing guide may be provided with a protrusion portion.
As illustrated in
At this time, when the sheet S is conveyed in a skewed state, the leading edge of the sheet S on the leading side in the width direction W first comes into contact with the conveyance nip N1. Then, the sheet S turns about the contact portion with the conveyance nip N1 that abuts first so that the leading edge Sa follows the conveyance nip N1.
As illustrated in
Therefore, the leading edge Sa of the sheet S whose skew has been corrected by following the conveyance nip N1 has a region abutting on the guide surface 52a and a region entering the recess portion 52b, and these regions have positions different from each other in the thickness direction of the sheet.
For example, when any two conveyance nips N1 and N1 on the center side in the width direction W are the first nip and the second nip, the leading edge Sa abuts against the first nip and the second nip, so that the skew of the sheet S is corrected. Then, the leading edge Sa of the sheet S is sandwiched between the recess portion 52b disposed between the conveyance nips N1 and N1 in the width direction W and the conveyance nips N1 and N1, and the leading edge Sa of the sheet S has a wavy shape. The leading edge Sa enters the recess portion 52b.
As described above, the leading edge Sa of the sheet S is sandwiched between the conveyance nip N1 and the protrusion portion 114a displaced in the width direction W and the thickness direction of the sheet, so that the leading edge Sa of the sheet S becomes into a wavy shape.
Further, since the sheet S is conveyed by the conveyance unit 4 even while the movement in the sheet conveyance direction CD is restricted by the conveyance nip N1, a loop is formed upstream of the leading edge Sa in the sheet conveyance direction CD. However, in the present embodiment, as described above, the cross section secondary moment of the sheet S is increased by waving the leading edge Sa of the sheet S, and the rigidity is temporarily improved. Therefore, even if the leading edge Sa is conveyed by the conveyance unit 4 in a state where the leading edge Sa is dammed by the conveyance nip N1, it is difficult to form a loop on the sheet S. That is, even if the registration roller pair 51 is stopped for the same time as the related art, the loop is less likely to be formed on the sheet S in the present embodiment than in the related art.
As illustrated in
As described above, in the present embodiment, by waving the leading edge Sa of the sheet S, the rigidity of the sheet S itself can be temporarily improved, and the loop formed on the sheet S at the time of skew correction can be reduced. Accordingly, the skew returning can be reduced, and the skew of the sheet can be satisfactorily corrected. In addition, the print image accuracy can be improved, and a good product can be obtained. In particular, for example, a sheet having a small grammage such as thin paper tends to have a large loop formed at the time of the skew correction, but according to the present embodiment, the skew can be satisfactorily corrected regardless of the grammage of the sheet. Furthermore, since the present embodiment has a simple configuration, the skew of the sheet can be corrected with an inexpensive configuration.
In the present embodiment, the swing guide 114 is swingably attached to the registration frame 52, but the present invention is not limited thereto. For example, the swing guide 114 may be mounted to be linearly movable with respect to the registration frame 52.
In any of the embodiments described above, each of the conveyance roller pair 41 and the registration roller pair 51 is constituted by a roller, but the present invention is not limited thereto. For example, some or all of the conveyance roller pair 41 and the registration roller pair 51 may be formed of another rotating member such as a belt.
In the first and second embodiments, the guide surface 52a and the recess portion 52b are provided in the registration frame 52, but the present invention is not limited thereto. For example, the guide surface 52a and the recess portion 52b may be provided in a member different from the registration frame 52. In the first embodiment, the skew correction member 531 is supported by the registration frame 52, but may be supported by another member.
In any of the embodiments described above, the electrophotographic printer 1 has been described, but the present invention is not limited thereto. For example, the present invention can also be applied to an inkjet type image forming apparatus that forms an image on a sheet by ejecting ink liquid from a nozzle. In addition, the above-described embodiments and modifications may be arbitrarily combined.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2022-064386, filed Apr. 8, 2022, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-064386 | Apr 2022 | JP | national |
