Patent Application
20150166284
The present invention relates to a sheet conveying device and an image forming apparatus including the same.
Exemplary devices for correcting any obliquity of a sheet that is being conveyed include a device (see PTL 1) that performs correction by using shutters 223 provided adjacent to pairs of rollers 218 and 219, respectively, as shown in a perspective view in
In the device shown in
In recent years, with demands for more improved throughput (the number of sheets per unit time on which images are formed) of image forming apparatuses from users, there have been demands for higher sheet conveyance speed and shorter interval from the trailing end of the preceding sheet to the leading end of the subsequent sheet (hereinafter referred to as “sheet interval”). In response to such demands, it has been desired that the shutters return to the standby position for aligning the leading end of the subsequent sheet again after the passage of the trailing end of the preceding sheet on the condition of a short sheet interval.
In the configuration employing the conventional shutters, the shutters are swingably provided on a conveying roller shaft and swing back and forth about the conveying roller shaft every time a sheet passes. Therefore, the minimum sheet interval necessary was to be a distance described as follows. The distance by which the contact surfaces 223a of the shutters 223 move from the position shown in
To increase the throughput of the image forming apparatus, it can be considered to increase the sheet conveyance speed, instead of reducing the sheet interval. An increase in the sheet conveyance speed, however, leads to a problem described below.
The distance D2 by which the subsequent sheet is conveyed during the returning motion of the shutters is a distance (ΔT×V=D2) calculated as the time ΔT during which the shutters 223 rotates from the position shown in
Hence, in the sheet conveying device that corrects any obliquity of the sheet by using the shutters, the degree of improvement of throughput in sheet conveyance (the number of sheets conveyable per unit time) is limited because of the restriction regarding the time required for the shutters to return to the standby position.
The present invention is to provide a sheet conveying device that realizes a short sheet interval and corrects any obliquity of the sheet, and an image forming apparatus including the same.
The present invention provides a sheet conveying device including a conveying section that conveys a sheet; a blocking member having a blocking surface with which a leading end of the sheet that is being conveyed by the conveying section comes into contact for obliquity correction; and a positioning unit that positions the blocking member to be in a standby position by applying an urging force to the blocking member. The leading end of the sheet that is being conveyed by the conveying section is blocked by coming into contact with the blocking surface of the blocking member in the standby position. The blocking member is rotated by being pushed by the sheet that is being conveyed by the conveying section against the urging force applied by the positioning unit. The blocking member is rotatable to be in a sheet-passage-allowing orientation in which the sheet is allowed to pass, and, after a trailing end of the sheet that is being conveyed has passed the blocking member, the blocking member that is in the sheet-passage-allowing orientation rotates in a same direction as a sheet conveyance direction and is positioned to be in the standby position.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Embodiments of the present invention will now be described with reference to the drawings. Herein, elements common to all the drawings are denoted by common reference numerals.
Referring to
Furthermore, cleaning means 6a to 6d that remove post-transfer toner remaining on the surfaces of the photoconductor drums 1 after the transfer, and so forth are provided. In this embodiment, the photoconductor drums 1, the charging means 2, the developing means 4, and the cleaning means 6 that remove toner integrally form process cartridges 7a to 7d.
The photoconductor drums 1, functioning as image bearing members, each include an aluminum cylinder whose outer peripheral surface is coated with an organic photoconductive layer (OPC). Each photoconductor drum 1 is rotatably supported by flanges at both ends thereof. A driving force from an unshown drive motor is transmitted to one end of the photoconductor drum 1, whereby the photoconductor drum 1 is driven to rotate counterclockwise in the drawing.
The charging means 2a to 2d are each a conductive roller having a roller shape. The roller is in contact with the surface of the photoconductor drum 1. Meanwhile, a charging bias voltage is applied to the roller by an unshown power supply. Thus, the surface of the photoconductor drum 1 is uniformly charged. The exposing means 3 each include a polygonal mirror. Image light corresponding to an image signal is applied to the polygonal mirror from an unshown laser diode.
The developing means 4a to 4d include toner containers 4a1, 4b1, 4c1, and 4d1; developing rollers 4a2, 4b2, 4c2, and 4d2; and so forth, respectively. The toner containers 4a1 to 4d1 contain toners of different colors, specifically, black, cyan, magenta, and yellow, respectively. The developing rollers 4a2 to 4d2 adjoin the surfaces of the respective photoconductor drums 1 and perform development by applying a development bias voltage while being driven to rotate.
A transfer belt 9a with which the sheet is conveyed upward is provided in such a manner as to face the four photoconductor drums 1a to 1d. The transfer members 5a to 5d are provided on the inside of the transfer belt 9a in such a manner as to face the four photoconductor drums 1a to 1d, respectively, and to be in contact with the transfer belt 9a. The transfer members 5a to 5d are connected with an unshown power supply for transfer bias. The transfer members 5 apply a positive charge to the sheet S through the transfer belt 9a. With the resulting electric field, the negatively charged toner images in the respective colors on the photoconductor drums 1 are sequentially transferred to the sheet S that is in contact with the photoconductor drums 1, whereby a color image is formed. A fixing unit 10 for fixing on the sheet the toner images transferred to the sheet is provided above the transfer belt 9a. A pair of discharge rollers 11 and 12 for discharging the sheet having the image formed thereon to a discharge portion 13 is provided above the fixing unit 10.
A feed unit 8 that feeds a sheet from a stack of sheets placed therein is provided at the bottom of the image forming apparatus 100. The feed unit 8 includes a pair of feed rollers 8a that feeds a sheet toward the transfer belt 9a. A pair of conveying rollers 91, which is a pair of rotatable members including a driving roller 19 and a conveying roller 18, is provided between the pair of feed rollers 8a, which form a conveying section conveying a sheet, and the transfer belt 9a. The pair of feed rollers 8a and the pair of conveyance rollers 91 form part of a sheet conveying device that conveys a sheet while correcting any obliquity of the sheet. The detailed configuration of the sheet conveying device will be described separately below.
Reference numeral 15 denotes a duplex conveyance path that connects the pair of discharge rollers 11 and 12 and the pair of conveying rollers 91. Oblique conveying rollers 16 and a U-turn roller 17 are provided in the duplex conveyance path 15.
The sheet S fed by the pair of feed rollers 8a of the feed unit 8 is conveyed to the transfer belt 9a by the pair of conveying rollers 91. While the sheet is conveyed by the transfer belt 9a, the toner images formed on the photoconductor drums 1a to 1d are sequentially transferred to the sheet by the operation of the transfer members 5a to 5d. The sheet having the toner images transferred thereto undergoes image fixing in the fixing unit 10 and is discharged to the discharge portion 13 by the pair of discharge rollers 11 and 12.
To form images on both sides of the sheet, the pair of discharge rollers 11 and 12 are rotated backward while the sheet is conveyed by the pair of discharge rollers 11 and 12, whereby the sheet is conveyed into the duplex conveyance path 15 by the pair of discharge rollers 11 and 12. The sheet S conveyed into the duplex conveyance path 15 passes the oblique conveying rollers 16 and is conveyed to the transfer belt 9a again by the U-turn roller 17 and the pair of conveying rollers 91. Subsequently, an image is formed on a second side of the sheet.
The configuration of the sheet conveying device according to this embodiment integrally included in the image forming apparatus 100 will now be described with reference to perspective views of the sheet conveying device shown in
Pairs of conveying rollers 91 include driving rollers 19 and conveying rollers 18. The driving rollers 19 are fixed on a driving shaft 19a extending parallel to the direction of the axes of rotation of the photoconductor drums 1. The driving shaft 19a is rotatably supported by a feed frame 20. A rotational driving force from an unshown motor is transmitted to the driving shaft 19a, whereby the driving rollers 19 rotate.
The conveying rollers 18 are arranged in the axial direction. The conveying rollers 18 are rotatably supported by the feed frame 20. The conveying rollers 18 are in contact with the driving rollers 19, respectively, whereby nips are formed. The sheet is conveyed while being nipped between the conveying rollers 18 and the driving rollers 19.
As shown in a perspective view in
The conveying rollers 18 are movably supported by the feed frame 20 and are urged against the driving rollers 19 by conveying roller springs 21 in such a manner as to be press-contactable with the driving rollers 19. The conveying roller springs 21 are fixed to the feed frame 20. In the state where the conveying rollers 18 are urged against the driving rollers 19, gaps are provided between the outer peripheral surface of the shutter shaft 22 and the inner peripheral surfaces defining the through-holes of the conveying rollers 18. Therefore, the spring forces of the conveying roller springs 21 are not transmitted to the shutter shaft 22. Hence, the spring forces of the conveying roller springs 21 do not prevent the rotational motions of the shutter members 23 and the shutter cam 24 both integrally fixed on the shutter shaft 22.
The shutter members 23, functioning as blocking members, each have four bumper surfaces 23a, 23b, 23c, and 23d provided at regular intervals in the peripheral direction. The bumper surfaces 23a, 23b, 23c, and 23d can block the sheet S by coming into contact with the leading end of the sheet S immediately before the sheet S enters the nips between the driving rollers 19 and the conveying rollers 18. The bumper surfaces 23a, 23b, 23c, and 23d, functioning as blocking surfaces, are provided such that, before the leading end of the sheet S comes into contact with the shutter members 23 at the relevant bumper surfaces, these bumper surfaces are positioned on the upstream side with respect to the nips between the driving rollers 19 and the conveying rollers 18 and block the leading end of the sheet that is being conveyed.
The shutter cam 24 will now be described. The shutter cam 24 determines the position of the shutter members 23 in the rotating direction and sets the bumper surfaces 23a, 23b, 23c, and 23d of the shutter members 23 to be at such appropriate positions as to block the leading end of the sheet. As shown in
As shown in cross-sectional views in
According to such a configuration, while the cam follower 26 urges the shutter cam 24 with the spring force of the shutter spring 27, the shutter members 23 are retained in a standby position (standby state) in the rotating direction, as shown in
In the cross-sectional views shown in
In this embodiment, the shutter shaft 22, the shutter members 23, and the shutter cam are molded as separate members, and the shutter members 23 and the shutter cam 24 are fixed on the shutter shaft 22. Alternatively, the shutter members, the shutter cam, and the shutter shaft may be provided as an integral resin molding.
The behavior of the sheet conveying device will now be described with reference to
Suppose that, for example, a sheet S conveyed by the feed unit 8 obliquely advances toward the pairs of conveying rollers 91 as shown in
Subsequently, when the leading end of the sheet comes into contact with the bumper surfaces 23a, the sheet S receives a reactive force produced by the retaining force of the shutter cam 24 urged by the shutter spring 27 and inertial forces, acting as reactive forces, of the shutter shaft 22 and the shutter members 23 and the shutter cam 24 both fixed on the shutter shaft 22. In this embodiment, in the state shown in
When the pair of feed rollers 8a of the feed unit 8 further convey the sheet S, a loop is formed near the leading end of the sheet as shown in
The behavior occurring when the leading end of the sheet is aligned with the bumper surfaces 23a of the shutter members 23 will now be described in detail. Specifically, a portion of the leading end of the sheet S advancing ahead in the sheet width direction is blocked in such a state as to be in contact with the bumper surface 23a of a corresponding one of the shutter members 23. Subsequently, portions of the leading end of the sheet S following behind in the sheet width direction sequentially come into contact with and are blocked by the bumper surfaces 23a of the other shutter members 23, respectively. More specifically, in the example shown as a top view in
With the above series of movements, the leading end of the sheet S is aligned with the bumper surfaces 23a of the shutter members 23, whereby the leading end of the sheet becomes parallel to the axis of rotation of the pairs of conveying rollers 91. Furthermore, after a specific loop is formed in the sheet S in a sheet conveyance path defined by the right conveyance guide 28 and the left conveyance guide 20b, the shutter members 23 rotate about the shutter shaft 22 in the direction of an arrow z shown in
The embodiment described above concerns a case where the shutter members 23 do not swing at the time the right side of the leading end of the sheet has just come into contact with a corresponding one of the shutter members 23, but the shutter members 23 start to swing when the left side of the leading end of the sheet has also come into contact with a corresponding one of the shutter members 23. Alternatively, the leading end of the sheet may be aligned with the bumper surfaces such that, while a portion of the leading end of the sheet that is in contact with a corresponding one of the shutter members 23 is causing the shutter member 23 to swing, the other portions of the leading end of the sheet sequentially come into contact with the bumper surfaces of the other shutter members 23 and are aligned therewith. Any obliquity can also be corrected with such a setting of the spring force of the shutter spring 27.
Subsequently, the shutter members 23 and the shutter cam 24 are further rotated by the leading end of the sheet S that is being conveyed by the driving rollers 19 and the conveying rollers 18. With the rotation of the shutter members 23 and the shutter cam 24, referring now to
Then, with the urging force of the shutter spring 27, the state of the shutter members 23 changes from the state shown in
After the trailing end of the sheet S has passed the pair of feed rollers 8a on the upstream side, the apparent stiffness of the sheet S is reduced. Therefore, after the trailing end of the sheet S has passed the pair of feed rollers 8a, the balanced state (
By repeatedly producing the states shown in
In this embodiment, the time from when the trailing end of a sheet has left the shutter members 23 until when the shutter members 23 move to be in the standby position for aligning the leading end of another sheet with the subsequent bumper surfaces thereof can be reduced. This is because the shutter members 23 rotate in the sheet conveyance direction from the state (
Depending on the number of sheets conveyed, the bumper surfaces of the shutter members may be scraped because the leading ends of sheets bump against the bumper surfaces. By providing a plurality of bumper surfaces for each of the shutter members as in this embodiment, the scraping of the bumper surfaces can be reduced.
Although the above embodiment employs a configuration in which each shutter member 23 has four bumper surfaces, the same advantageous effect can be produced by other configurations in which one to three bumper surfaces are provided in accordance with the tolerable levels of the number of conveyable sheets that are required in individual sheet conveying devices. The shapes of the shutter members 23 and the shutter cams 24 in such configurations are shown in
Referring to
Referring now to
In a case where the sheet to be used has a relatively small width that does not cover the shutter members 23E and 23H (the sheet S2 shown by a dashed line in
By providing the shutter members 23F and 23G, the contact pressure produced at the bumper surfaces where the leading end of the sheet comes into contact with the shutter members can be reduced. This prevents the occurrence of local dents in the sheet having a relatively large width produced when the leading end of the sheet comes into contact with the shutter members.
To obtain more precise correctability for any obliquity of the sheet S, the distance between the shutter members 23 corresponding to the width of the sheet S is preferably as long as possible, and the shutter members 23 are preferably arranged substantially symmetrically with respect to the center in the widthwise direction of the sheet S. This is because the error in the angle of correction of the leading end of the sheet S with respect to the direction of the axis of rotation of the driving rollers 19 is to be reduced.
Considering the above, shutter members 23 are preferably provided at positions corresponding to both side ends of the sheet S to be conveyed. Furthermore, to enable the correction of any obliquity of a sheet S having a relatively small width, additional shutter members 23 are preferably provided near the center C in the widthwise direction of the sheet S. That is, a plurality of shutter members 23 are preferably provided in the widthwise direction. Here, the distance between the two shutter members 23F and 23G that are nearest to and on both sides of the widthwise center C is set to be smaller than the minimum width of the sheet S to be used in the image forming apparatus. In this case, it is also preferable that the bumper surfaces of the shutter members 23F and 23G provided near the widthwise center be positioned on the downstream side in the sheet conveyance direction with respect to those of the shutter members 23E and 23H provided near both ends in the widthwise direction.
It is also preferable that the distance between the relevant one of the bumper surfaces 23a, 23b, 23c, and 23d of each shutter member 23 in the standby position and the corresponding nip between the driving roller 19 and the conveying roller 18 be as short as possible as in this embodiment. Thus, immediately before the leading end of the sheet S is taken into and nipped at the nips between the driving rollers 19 and the conveying rollers 18, the leading end of the sheet S is blocked by bumping against relevant ones of the bumper surfaces 23a to 23d, whereby any obliquity of the sheet S is corrected. According to such a configuration, immediately after any obliquity of the sheet S is corrected by the shutter members 23, the sheet S is nipped at the nips between the driving rollers 19 and the conveying rollers 18 and is conveyed. Therefore, while the effect of correction of any obliquity of the sheet by the shutter members 23 produced when the leading end of the sheet bumps against the shutter members 23 is maintained, the leading end of the sheet can be nipped between the driving rollers 19 and the conveying rollers 18 more assuredly.
It is also preferable that a plurality of bumper surfaces with which the shutter members come into contact with the leading end of the sheet be arranged in the direction orthogonal to the sheet conveyance direction and substantially symmetrically with respect to the widthwise center of the sheet. In such a case, more precise correctability for any obliquity of the sheet can be obtained. Furthermore, the occurrence of local dents in the sheet produced when the sheet comes into contact with the shutter members 23 can be prevented.
A second embodiment of the sheet conveying device and an image forming apparatus including the same according to the present invention will now be described with reference to
The configuration according to the second embodiment will first be described with reference to the perspective view shown in
Meanwhile, as shown in
The behavior occurring in the second embodiment will now be described with reference to
A force that rotates the shutter members 23 and the rotating cam 29 about the shutter shaft 22 in the direction of the arrow z shown in
When the shutter members 23 and the rotating cam 29 further rotate, the leading end of the sheet S is nipped at the nips between the driving rollers 19 and the conveying rollers 18 and is conveyed. The sheet S conveyed with the conveyance force of the conveying rollers 18 and the driving rollers 19 causes the shutter members 23 and the rotating cam 29 to further rotate. Subsequently, as shown in
When the trailing end of the sheet S has left the shutter members 23, the shutter members 23 rotate to be in the standby position again for aligning the leading end of the subsequent sheet (the leading end of the subsequent sheet is to come into contact with the bumper surfaces 23b), as in the first embodiment. Here, the rotating cam 29, the sliding cam 30, and the pressing spring 31 are in the state shown in
By repeatedly producing the states described above, the shutter members 23 and the rotating cam 29 both fixed on the shutter shaft 22 rotate together with the shutter shaft 22. Furthermore, while sheets S are sequentially conveyed, the bumper surfaces that are positioned near the nips of the pairs of conveying rollers 91 change in the order of 23a, 23b, 23c, 23d, and 23a, as in the first embodiment. The leading end of each newly conveyed sheet S comes into contact with the relevant bumper surfaces, whereby any obliquity of each of the sheets S is corrected.
Advantageous effects produced in the first and second embodiments will now be summarized.
The retaining force acting to retain the shutter members 23 to be in the standby position and required for aligning the leading end of the sheet with the shutter members 23 is produced by the shutter spring 27 or the pressing spring 31, which is urging means, through the intermediary of the shutter cam 24 or the rotating cam 29. With this force, the leading end of the sheet is blocked by the shutter members 23, and a loop is formed in the sheet. With the loop formed in the sheet, the leading end of the sheet is aligned with the shutter members 23.
When the degree of stiffness of the sheet becomes higher than the degree of the retaining force of the shutter spring 27 or the pressing spring 31 that operates to retain the shutter members to be in the standby position, the sheet causes the shutter members 23 to rotate. While a state where the leading end of the sheet is in contact with the shutter members 23 is maintained, the leading end of the sheet is nipped by the pairs of conveying rollers 91. Since the leading end of the sheet is nipped by the pairs of conveying rollers 91 while the state where the leading end of the sheet is in contact with the shutter members 23 is maintained, the sheet nipped by the pairs of conveying rollers 91 has any obliquity thereof corrected.
The loop forming space 32 defined by the right conveyance guide 28 and the left conveyance guide 20b is provided on the upstream side in the conveyance direction with respect to the shutter members 23. With the loop forming space 32, a loop is easily formed in the sheet after the leading end of the sheet is blocked by the shutter members 23. On the upstream side with respect to the shutter members 23, there are variations in the sheet conveyance speed because of contact resistances produced by the conveyance guides and acting on the sheet that is being conveyed, component tolerances of the pair of feed rollers 8a, and so forth. Even in such a case where there are variations in the sheet conveyance speed, the difference in the sheet conveyance speed seen on the upstream side in the sheet conveyance direction with respect to the shutter members 23 is eliminated in the loop forming space 32 that realizes easy formation of a loop in the sheet, and a loop necessary for obliquity correction is formed in the sheet. Moreover, since the looped portion of the sheet comes into contact with the right conveyance guide 28 defining the loop forming space 32, the sheet can have a sufficient degree of strength required for the leading end thereof to rotate the shutter members 23. Therefore, such kinds of failure are prevented that the shutter members 23 are rotated by the sheet not having a sufficient loop and that the shutter members 23 cannot be rotated even by the sheet having a specific stiffness and a jam occurs.
When the trailing end of the sheet passes the shutter members 23, the shutter members 23 that have been in the sheet conveyance orientation (see
The spring force of the shutter spring 27 or the pressing spring 31 is utilized for causing the shutter members 23 in the state where the leading end of the sheet is in contact therewith (
Gaps are provided between the outer peripheral surface of the shutter shaft 22 provided for the shutter members 23 and the inner peripheral surfaces defining the through-holes of the conveying rollers 18. Therefore, the spring forces of the conveying roller springs 21 are not transmitted to the shutter shaft 22. Hence, the spring forces of the conveying roller springs 21 do not prevent the rotational motions of the shutter members 23 integrally fixed on the shutter shaft 22. Accordingly, the retaining force acting to retain the shutter members 23 to be in the standby position and required for aligning the leading end of the sheet with the shutter members 23 can be produced stably. Furthermore, the rotational force acting to rotate the shutter members in the same direction as the sheet conveyance direction and to bring the shutter members to be in the standby position quickly after the trailing end of the sheet has passed the shutter members can be produced stably.
A third embodiment of the sheet conveying device and an image forming apparatus including the same according to the present invention will now be described with reference to FIGS. 13 to 15B-2. Herein, configurations different from those in the first embodiment are only described, and configurations identical with those in the first embodiment are denoted by the corresponding reference numerals, whereby descriptions thereof are omitted.
The third embodiment differs from the first embodiment in that a detecting member 34 is provided on the shutter shaft 22 according to the first embodiment and a detection sensor 33 that detects the movement of the detecting member 34 is added.
As shown in a perspective view in
The behavior occurring in the third embodiment will now be described with reference to FIGS. 14A to 15B-2.
Subsequently, after the leading end of the sheet S that is being conveyed has come into contact with the bumper surfaces 23a, the leading end of the sheet S is nipped by the pairs of conveying rollers 91 and the sheet S starts to be conveyed by the pairs of conveying rollers 91, as shown in
Subsequently, as in the first embodiment, when the trailing end of the sheet S has left the shutter members 23, the shutter members 23 rotate to be in the standby position. The detecting member 34 stands by again, as are the shutter members 23, in the standby position shown in
As described above, the detecting member 34 behaves similarly to the shutter members 23 according to the first embodiment. Therefore, almost at the same time as the trailing end of a sheet S leaves the shutter members 23, the detecting member 34 can be in the standby position for detecting the leading end of the subsequent sheet S. Thus, even under the condition of a high sheet conveyance speed and with a short sheet interval, the detecting member 34 can return to the home position for detecting the leading end of the subsequent sheet. Accordingly, users' demands for more improved throughput of image forming apparatuses can be met.
The configuration described in the third embodiment in which the sheet that is being conveyed is detected by detecting the position of the shutter members with the detection sensor can also be applied to the second embodiment. Specifically, in the second embodiment, an intercepting member that intercepts the optical path of the detection sensor is provided on a shutter member 23. The intercepting member on the shutter member 23 is set in such a manner as not to intercept the optical path of the detection sensor when the shutter members 23 are in the standby position, and to intercept the optical path of the detection sensor 33 while the shutter members are rotating by being pushed by the sheet that is being conveyed by the pairs of conveying rollers 91.
This embodiment also produces the same advantageous effects as in the first and second embodiments. Moreover, this embodiment produces the following advantageous effect. Since the detecting member for turning the detection sensor 33 on and off moves in conjunction with the shutter members 23 so as to detect the sheet, the detecting member can be quickly positioned to be in the standby position for detecting the subsequent sheet.
A fourth embodiment of the sheet conveying device and an image forming apparatus including the same according to the present invention will now be described with reference to
The projecting amount of the convex portions 23j, 23k, 23l, and 23m in the radial direction is smaller than the projecting amount of the portions having the bumper surfaces 23a, 23b, 23c, and 23d of the shutter member and forming the outermost portions on the contour of the shutter member in the radial direction. In addition, the convex portions 23j, 23k, 23l, and 23m projecting by the above amount in the radial direction extend more outward than the contour of the conveying roller 18. That is, the tops of the convex portions 23j, 23k, 23l, and 23m are positioned on the outer side of the contour of the conveying roller 18.
The behavior occurring in the fourth embodiment will now be described with reference to
Subsequently, when the sheet is conveyed by the pairs of conveying rollers 91, the shutter members 23 that are in the state shown in
The advantageous effect brought by the convex portions 23j, 23k, 23l, and 23m added in the fourth embodiment will now be described. After the leading end of a sheet has come into contact with the bumper surfaces 23a of the shutter members 23, the shutter members 23 rotate with the rotational force of the shutter cam 24 and the shutter members 23 come into contact with the sheet S. The noise produced by the contact can be reduced compared to that in the first embodiment. The reason for this will be described below in detail.
In the first embodiment, when the shutter members 23 rotate with the rotational force of the shutter cam 24, the shutter members 23 each come into contact with the sheet S at a point (corresponding to an end portion 23i in
In contrast, in the fourth embodiment, each shutter member 23 comes into contact with the sheet S at the convex portion 23k. Here, the contact radius from the contact point (convex portion) between the sheet S and each shutter member 23 to the center of rotation of the shutter member 23 is denoted by R2, and the angular speed of the shutter member 23 at the contact point is denoted by ω2. Then, the contact speed V2 at which the shutter member 23 comes into contact with the sheet S is expressed as V2=R2·ω2. The relationship between the contact radii in the first and fourth embodiments is such that the contact radius R2 is smaller than the contact radius R1 as shown in
The angular speed will now be described with reference to
As shown in
The contact energy E with which the shutter members 23 subjected to the rotational force of the shutter cam 24 come into contact with the sheet S is proportional to the second power of the contact speed. Hence, the relationship between the contact energy E1 in the first embodiment and the contact energy E2 in the fourth embodiment is expressed as E2=0.41·E1. By adding the convex portions, the contact energy can be reduced by about 60% from that in the first embodiment. If the contact energy is reduced, the contact noise is also reduced. According to an experiment performed under the above conditions, the contact noise in the first embodiment was 58 dB, and the contact noise in the fourth embodiment was 53 dB. That is, the contact noise was reduced by 5 dB.
As described above, by integrally forming on each shutter member 23 the convex portions 23j, 23k, 23l, and 23m with one of which the surface of the sheet comes into contact, the contact noise generated when the surface of the sheet conveyed by the pairs of conveying rollers 91 comes into contact with the shutter members 23 can be reduced. Thus, a sheet conveying device generating less noise and realizing improved throughput can be provided to users.
In the above embodiment, the convex portions 23j, 23k, 23l, and 23m are integrally formed on each of the shutter members 23. Alternatively, the convex portions 23j, 23k, 23l, and 23m may be provided as separate components and are connected to the shutter members 23 with elastic members such as springs or the like. Furthermore, the convex portions may be provided by forming gentle slopes extending from the tips of each shutter member 23 as shown in
The configuration described in the fourth embodiment in which the convex portions are provided on the shutter members 23 can also be applied to the second or third embodiment.
A fifth embodiment of the sheet conveying device and an image forming apparatus including the same according to the present invention will now be described with reference to
In the first to fourth embodiment, the shutter members are rotated in the same direction as the sheet conveyance direction by causing the cam fixed on the shutter shaft to be pressed with a compression spring. In the fifth embodiment, the driving force from the motor, which is a drive unit, is transmitted through a partially toothless gear fixed on the shutter shaft 22. With the driving by the motor, the shutter members are rotated in the same direction as the sheet conveyance direction so as to be in the standby position.
The configuration according to the fifth embodiment will first be described. The shutter members 23 are fixed on the shutter shaft 22. In the fifth embodiment, the conveying rollers 18 are supported by the feed frame, and the shutter shaft 22 extends through the conveying rollers 18 and is rotatably supported by the feed frame, as in the first embodiment.
A partially toothless gear 36 is fixed to one end of the shutter shaft 22 with a spring pin or the like. The partially toothless gear 36, which rotates together with the shutter shaft 22 and the shutter members 23, has on the outer periphery thereof a toothless portion 36a where no teeth are provided. The partially toothless gear 36 can mesh with a driving gear 37 functioning as a transmission gear and provided on the driving shaft 19a for the driving rollers 19, which are rotatable driving members. The partially toothless gear 36 and the driving gear 37 in combination form a driving-force-transmitting mechanism that transmits a driving force for rotating the shutter members 23. That is, the partially toothless gear 36 and the driving gear 37 transmit the driving force from the motor, which is a drive unit that rotates the driving rollers 19, so as to rotate the shutter members 23. A tension spring 35, functioning as urging means, is stretched to the partially toothless gear 36. An urging force produced by the tension spring 35 in accordance with the position of the partially toothless gear 36 in the rotating direction acts on the shutter shaft 22 and the shutter members 23 through the partially toothless gear 36. This embodiment concerns a configuration in which the tension spring 35 is stretched to the partially toothless gear 36. Alternatively, the tension spring may be stretched to another component fixed on the shutter shaft 22 or to a shutter member 23.
The behavior occurring in the fifth embodiment will now be described.
When the leading end of the sheet S comes into contact with the bumper surfaces 23a, a loop is formed in the sheet S, and the shutter shaft 22 and the shutter members 23 are rotated by the sheet S having a specific stiffness. That is, the sheet causes the shutter shaft 22 and the shutter members 23 to rotate in such a direction as to retract from the sheet conveyance path against the urging force of the tension spring 35. In this process, the leading end of the sheet is aligned with the bumper surfaces of the shutter members 23, as in the embodiments described above.
While the leading end of the sheet is pushing the shutter members 23, the leading end of the sheet is nipped between the driving rollers 19 and the conveying rollers 18. Along with the rotation of the shutter members 23, the partially toothless gear 36 fixed on the shutter shaft 22 rotates together with the shutter shaft 22. When the leading end of the sheet S has reached the downstream side with respect to the nips between the driving rollers 19 and the conveying rollers 18, referring now to
When the partially toothless gear 36 is rotated by the driving gear 37 in the above state to be in a position in which the toothless portion 36a thereof faces the driving gear 37 as shown in
The shutter members 23 that are in the sheet-passage-allowing orientation in which the sheet is allowed to pass, as shown in
Thus, for every conveyance of a sheet, the shutter shaft 22 together with the shutter members 23 and the partially toothless gear 36 fixed on the shutter shaft 22 rotate in the same direction as the sheet conveyance direction in such a manner as to sequentially produce the states shown in
A sixth embodiment of the sheet conveying device and an image forming apparatus including the same according to the present invention will now be described with reference to
In the fifth embodiment, the conveying rollers 18 are supported by the feed frame and the shutter members are fixed on the shutter shaft 22 extending through the conveying rollers 18, whereby the shutter shaft and the shutter members rotate together about the center of rotation of the conveying rollers. In contrast, in the sixth embodiment, the conveying rollers 18 are fixed on a conveying roller shaft 39 that is supported by the feed frame, and the shutter members are rotatably supported by the conveying roller shaft 39.
The configuration according to the sixth embodiment will now be described in detail with reference to the perspective view shown in
In the sixth embodiment, the conveying roller shaft 39 supports shutter members 38. The shutter members 38 are supported in such a manner as to be rotatable with respect to the conveying roller shaft 39. The conveying roller shaft 39 is provided with the conveying rollers 18 arranged thereon in the axial direction. The shutter members 38 are provided with gear portions 38a, respectively, integrally formed thereon.
The shutter members 38 are set to be in phase with each other by a shutter driving shaft 41 provided separately from the driving shaft 19a and the conveying roller shaft 39. Specifically, a plurality of shutter driving gears 42 are fixed on the shutter driving shaft 41 and are arranged in the axial direction at the same intervals as those of the shutter members 38. The shutter driving gears 42 mesh with the gear portions 38a of the shutter members, respectively. Furthermore, an idler gear 43 is fixed at one end of the shutter driving shaft 41. The idler gear 43 can mesh with a partially toothless gear 40. The idler gear 43 and the shutter driving gears 42 have the same number of teeth. The partially toothless gear 40 can mesh with the driving gear 37 functioning as a transmission gear. The driving gear 37, the partially toothless gear 40, the idler gear 43, the shutter driving shaft 41, the shutter driving gears 42, and the gear portions 38a in combination form a driving-force-transmitting mechanism for transmitting a driving force for rotating the shutter members 38.
In the sixth embodiment, the transmission of the driving force to the shutter members 38 and the stoppage of the transmission are realized by the partially toothless gear 40 and the tension spring 35 stretched thereto, as in the fifth embodiment. In the sixth embodiment, a toothless portion 40a of the partially toothless gear 40 only extends halfway in the tooth width direction (axial direction). The meshing between the driving gear 37 and the partially toothless gear 40 is released at the toothless portion 40a. Whereas, the idler gear 43 provided on the shutter driving shaft 41 constantly meshes with the partially toothless gear 40, thereby rotating constantly together with the partially toothless gear 40.
The behavior occurring in the sixth embodiment is similar to that in the fifth embodiment, in which the transmission of the driving force and the stoppage of the transmission are performed repeatedly, and the shutter members 38 repeatedly rotate in the same direction as the sheet conveyance direction for every conveyance of a sheet.
That is, when the shutter members 38 are in the standby position, the toothless portion 40a of the partially toothless gear 40 faces the driving gear 37. When the leading end of a sheet S that is being conveyed comes into contact with the bumper surfaces of the shutter members 38, the sheet S is blocked with the urging force of the tension spring 35, whereby a loop is formed in the sheet. The shutter members 38 rotate with respect to the conveying roller shaft 39 with a specific stiffness of the sheet S. When the shutter members 38 rotate by being pushed by the sheet that is being conveyed, the shutter members 38 having the gear portions 38a rotate, and the shutter driving gears 42 meshing with the gear portions 38a rotate. When the shutter driving gears 42 rotate, the partially toothless gear 40 rotates through the intermediary of the idler gear 43.
When the leading end of the sheet S nipped by the driving rollers 19 and the conveying rollers 18 has reached the downstream side with respect to the nips between the driving rollers 19 and the conveying rollers 18, the partially toothless gear 40 and the driving gear 37 mesh with each other. When the partially toothless gear 40 and the driving gear 37 mesh with each other, the driving force of the motor for rotating the driving shaft 19a is transmitted from the driving gear 37 to the partially toothless gear 40, causing the shutter members 38 to rotate in the sheet conveyance direction through the intermediary of the idler gear 43 and the shutter driving gears 42.
When the toothless portion 40a of the partially toothless gear 40 faces the driving gear 37 while the shutter members 38 are rotating in such a manner, the transmission of the driving force from the driving gear 37 to the shutter members 38 is stopped. Then, the shutter members 38 subjected to the urging force of the tension spring 35 receive such a rotational force that the shutter members 38 are rotated toward the standby position, i.e., in the counterclockwise direction. As in the fifth embodiment, even though the rotational force acting to rotate the shutter members 38 counterclockwise is applied to the shutter members 38, the rotation of the shutter members 38 is prevented because the shutter members 38 are in contact with the surface of the sheet before the trailing end of the sheet S passes the shutter member 38. When the sheet is further conveyed and the trailing end of the sheet has left the shutter members 38, the shutter members 38 subjected to the urging force of the tension spring 35 rotate counterclockwise to be in the standby position, thereby being prepared for the subsequent sheet.
In the sixth embodiment, the conveying rollers 18 are supported by the conveying roller shaft 39, and the conveying rollers 18 are pressed against the driving rollers 19 such that the conveying roller shaft 39 is urged against the driving rollers 19 with an unshown spring. Therefore, even in a case where a shutter shaft on which the shutter members are to be fixed cannot be provided in conjunction with the conveying rollers 18, the bumper surfaces of the shutter members 38 can be oriented in phase with each other, and the driving force for rotating the shutter members 38 in the same direction as the sheet conveyance direction can be transmitted.
This embodiment concerns a configuration in which the shutter members 38 are supported by the conveying roller shaft 39. Alternatively, the shutter members 38 may be supported by the driving shaft 19a.
In each of the fifth and sixth embodiments, the detecting member operating in conjunction with the shutter members 23 or 38 and turning the detection sensor 33 on and off may also be provided so that the sheet is detected, as described in the third embodiment.
According to the present invention, after the leading end of a sheet that is being conveyed comes into contact with the blocking surface of the blocking member that is in the standby position and when the trailing end of the sheet has passed the blocking member from the sheet-passage-allowing orientation in which the sheet is allowed to pass, the blocking member rotates in the sheet conveyance direction and is positioned to be in the standby position. Therefore, the throughput in sheet conveyance can be improved.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/JP2009/068078 | Oct 2009 | JP | national |
This application is a Continuation of U.S. patent application Ser. No. 14/088,965 filed on Nov. 25, 2013, which is a Continuation of U.S. patent application Ser. No. 13/693,732 filed on Dec. 4, 2012, now U.S. Pat. No. 8,616,548, which is a Continuation of U.S. patent application Ser. No. 12/904,021 filed on Oct. 13, 2010, now U.S. Pat. No. 8,342,519, which claims the benefit of International Application No. PCT/JP2009/068078, filed Oct. 20, 2009, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14088965 | Nov 2013 | US |
| Child | 14626819 | US | |
| Parent | 13693732 | Dec 2012 | US |
| Child | 14088965 | US | |
| Parent | 12904021 | Oct 2010 | US |
| Child | 13693732 | US |
