Patent Grant
10023417
The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2015-113136 filed in Japan on Jun. 3, 2015. The contents of which are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a sheet post-processing apparatus and an image forming system.
2. Description of the Related Art
For example, there is a known sheet post-processing apparatus that temporarily stacks, on a stack tray, sheets conveyed from an image forming apparatus, performs a binding process on a sheet bundle that is a stack of a predetermined number of sheets, and then discharges the sheet bundle.
A sheet conveyed onto the stack tray comes in contact with a roller member that rotates in a direction in which the sheet is fed back toward an upstream side in a conveying direction, so that the motion of the sheet is damped and the sheet falls onto the stack tray. Subsequently, the sheet is conveyed to the upstream side in the conveying direction on the stack tray by the roller member and a rear end of the sheet butts against a rear-end-position regulating member, so that the sheet is aligned in the conveying direction.
The rotation speed of the roller member is constant without a change between when the sheet falls and when the sheet is conveyed to the rear-end-position regulating member.
Japanese Patent Laid-open Publication No. 2009-227468 discloses a technology, in which the speed of a rotation member for conveying a sheet to a rear-end-position regulating member is reduced relative to the rotation speed of a roller member for causing a sheet to fall onto a stack tray, in order to prevent buckling that occurs when the sheet is excessively conveyed backward.
The state of a sheet that is falling onto a stacking surface of the stack tray is unstable in the air. Therefore, if a conveying force is applied to the sheet by the roller member, a landing position of the sheet fluctuates.
If the rear end of the landed sheet is too close to the rear-end-position regulating member, the sheet is excessively conveyed at the time of rear-end butting, and sheet buckling occurs.
In contrast, if the rear end of the landed sheet is too far from the rear-end-position regulating member, the rear end of the sheet may not be conveyed to the rear-end-position regulating member, and a binding failure may occur.
In Japanese Patent Laid-open Publication No. 2009-227468, the influence of the roller member while the sheet is falling onto the stack tray is not considered.
In view of the above circumstances, there is a need to provide a sheet post-processing apparatus capable of stabilizing a landing state of a sheet on a stack tray, and contributing to sheet alignment accuracy and post-processing accuracy.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to exemplary embodiments of the present invention, there is provided a sheet post-processing apparatus comprising: a stack tray for stacking a sheet; a rear-end-position regulating member, against which a rear end of the sheet stacked on the stack tray is butted to align a position of the sheet in a conveying direction in which the sheet is conveyed toward the stack tray, the rear end of the sheet being a rear end in the conveying direction; and a roller member that comes in contact with an upper surface of a sheet conveyed to an upper side of the stack tray, before the sheet is stacked on a stacking surface on the stack tray, and conveys the sheet stacked on the stacking surface toward the rear-end-position regulating member, wherein a rotation speed before stacking, which is a rotation speed of the roller member when the roller member is in contact with the sheet while the rear end of the sheet in the conveying direction is not landed on the stacking surface, is set to be smaller than a rotation speed after stacking, which is a rotation speed of the roller member when the roller member conveys the sheet to the rear-end-position regulating member while the sheet is stacked on the stacking surface, and the rotation speed of before stacking is greater than zero.
Exemplary embodiments of the present invention also provide an image forming system comprising: an image forming apparatus that forms an image on a sheet based on image information; and a sheet post-processing apparatus, wherein the sheet post-processing apparatus comprises; a stack tray for stacking the sheet; a rear-end-position regulating member, against which a rear end of the sheet stacked on the stack tray is butted to align a position of the sheet in a conveying direction in which the sheet is conveyed toward the stack tray, the rear end of the sheet being a rear end in the conveying direction; and a roller member that comes in contact with an upper surface of the sheet conveyed to an upper side of the stack tray, before the sheet is stacked on a stacking surface on the stack tray, and conveys the sheet stacked on the stacking surface toward the rear-end-position regulating member, wherein a rotation speed before stacking, which is a rotation speed of the roller member when the roller member is in contact with the sheet while the rear end of the sheet in the conveying direction is not landed on the stacking surface, is set to be smaller than a rotation speed after stacking, which is a rotation speed of the roller member when the roller member conveys the sheet to the rear-end-position regulating member while the sheet is stacked on the stacking surface, and the rotation speed of before stacking is greater than zero.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of the present invention will be described below with reference to the drawings.
An overview of a configuration of an image forming system according to the first embodiment will be described based on
The image forming apparatus 4 is a conventionally-known electrophotography image forming apparatus, and is configured to form an electrostatic latent image based on image information on an image bearer by an exposing unit, develop the electrostatic latent image by a developing unit, eventually transfer the developed toner image to a recording medium (hereinafter, referred to as a sheet or paper), and fix the image by a fixing unit.
The sheet post-processing apparatus 6 may be integrated with the image forming apparatus 4 or may be detachably connected to the image forming apparatus 4.
An image-formed sheet discharged from the image forming apparatus 4 enters a first conveying path 10 of the sheet post-processing apparatus 6 through a connection port 8. On the first conveying path 10, an entrance roller pair 12 and an entrance sensor 14 are arranged, and the entrance sensor 14 detects that a sheet is conveyed into the sheet post-processing apparatus 6.
On the downstream side of the entrance roller pair 12, a punching unit 16 that punches a hole in the sheet is arranged. On the downstream side of the punching unit 16, a conveying roller pair 18 is arranged.
The downstream side of the conveying roller pair 18 is bifurcated into a second conveying path 20 extending upward and a third conveying path 22 as an extended path of the first conveying path 10.
In a bifurcation area of the second conveying path 20 and the third conveying path 22, a first bifurcating claw 24 is provided. By controlling rotation of the first bifurcating claw 24, a sheet is selectively guided to one of the conveying paths.
The sheet guided to the second conveying path 20 is conveyed by a conveying roller pair 26, and discharged to a proof tray 30 by a paper ejection roller pair 28.
A fourth conveying path 32 is branched from the third conveying path 22. By controlling rotation of a second bifurcating claw 34, a sheet is selectively guided to the fourth conveying path 32. The sheet guided to the fourth conveying path 32 is conveyed by a pre-stack roller pair 36.
On the third conveying path 22, an intermediate conveying roller pair 40 for conveying a sheet to an end binding unit 38 is arranged. In the vicinity of the upstream side of the intermediate conveying roller pair 40, an intermediate conveying sensor 42 that detects a sheet is arranged.
The sheet is ejected on a staple tray 44, which is a stack tray, by the intermediate conveying roller pair 40. A tapping roller 46 as a roller member is arranged above the staple tray 44. A rear end stopper 48 as a rear-end-position regulating member is arranged on the upstream side of the staple tray 44 in a sheet conveying direction.
The tapping roller 46 as one of aligning members performs a pendulum motion to thereby come in contact with a sheet, drop the sheet onto the staple tray 44 with high landing accuracy, and convey the sheet toward the rear end stopper 48.
A rear end of the sheet conveyed by the tapping roller 46 is butted against the rear end stopper 48 by a returning roller 50 as a butting member that is another one of the aligning members, so that the position of a sheet bundle in the conveying direction is aligned. The returning roller 50 is capable of coming in contact with and away from a stacking surface.
The rear end of the sheet means a rear end of a sheet in the conveying direction when the sheet is conveyed toward the staple tray 44.
On the staple tray 44, a pair of jogger fences 52 is provided. The jogger fences 52 move back and forth in a sheet width direction (lateral direction) perpendicular to the sheet conveying direction and align the position of a sheet ejected on the staple tray 44 in the sheet width direction.
Through the above-described two operations, sheets ejected on the staple tray 44 are stacked in an aligned manner. As for the aligned sheet bundle, in a staple mode, an end binding stapler 54 moves in the sheet width direction and binds an appropriate portion in a lower edge area of the aligned sheet bundle.
The sheet bundle (paper bundle) subjected to a binding process is discharged onto a paper ejection tray 60 by a discharging claw 58 that is moved by a belt conveying unit 56. The belt conveying unit 56 includes supporting rollers 56a and 56b and a belt 56c.
When the sheet bundle is discharged, the sheet bundle is stably discharged by being sandwiched by a paper ejection roller 62 and a driven roller 64.
With reference to
As illustrated in
An image-formed sheet 66 conveyed from the image forming apparatus 4 passes through the intermediate conveying roller pair 40 and is conveyed to the upper side of the staple tray 44.
At a timing at which the intermediate conveying sensor 42 detects a rear end of the sheet 66, the tapping roller 46 starts to perform a tapping operation.
That is, as illustrated in
The stacking surface indicates a stacking surface of the staple tray 44 when a sheet is not present on the staple tray 44, and indicates a surface of the topmost sheet when sheets are present on the staple tray 44.
As illustrated in
As illustrated in
The above-described stack operation will be described in detail below with reference to a timing diagram.
As illustrated in
The rotation speed before stacking is a rotation speed of the rotation roller 46a when the rotation roller 46a is in contact with a sheet while the rear end of the sheet in the conveying direction is not landed on the stacking surface.
After a predetermined time t2 (ms) since the landing of the rotation roller 46a on the staple tray 44 via the sheet 66, the rotation roller 46a is rotated at a rotation speed b (rpm), which is a rotation speed after stacking.
It is assumed that the rotation speed b (rpm) is a rotation speed with a conveying force to cause the rotation roller 46a to guide the sheet 66 to the rear end stopper 48.
It is also assumed that the rotation speed a is lower than the rotation speed b and has a value grater than 0 (rpm) in order to prevent a sheet from adhering to the stacking surface of the staple tray 44.
That is, the rotation speed a is a speed to apply, to the sheet 66 in an unstable state in the air above the staple tray 44, the minimum rotation force needed to prevent the sheet from adhering to the stacking surface. Consequently, it becomes possible to cause the sheet 66 to stably land on the staple tray 44.
As illustrated in
Subsequently, as illustrated in
The above-described stack operation is repeated for each sheet conveyed by the intermediate conveying roller pair 40. Fluctuation of the landing position of the sheet on the staple tray 44 can be prevented because of the low rotation speed a of the rotation roller 46a, so that the accuracy of rear-end alignment by the contact with the rear end stopper 48 can be improved.
As a result, it is possible to improve alignment accuracy of a sheet bundle on the staple tray 44, enabling to improve post-processing accuracy.
The above-described stack operation is performed on the first sheet. When sheets are stacked on the staple tray 44, a timing at which the rotation roller 46a comes in contact with the stacking surface is changed. To prevent reduction in the accuracy caused by a change in the timing, at least one of the predetermined times t1 and t2 is changed for each number of stacked sheets. By doing so, it is possible to obtain the same alignment accuracy as the first sheet, with respect to the other sheets.
For the same purpose, it may be possible to change the predetermined times t1 and t2 depending on a sheet type (thickness or the like) that is set or detected.
Furthermore, it may be possible to provide a stack height detecting unit that detects a height of a stack of sheets on the staple tray 44, and change the predetermined times t1 and t2 based on detection information obtained from the stack height detecting unit. As the stack height detecting unit, for example, it may be possible to arrange a reflective optical sensor 68 on the upper surface of the rear end stopper 48 and detect a height of a stack that is changed depending on the number of stacked sheets.
As the stack height detecting unit, it may be possible to use a mechanical detecting unit, which is conventionally used to detect a height of a stack on a paper ejection tray.
If the low rotation speed a is rapidly changed to the high rotation speed b, a sheet surface may be damaged depending on a material of the sheet. The second embodiment is conceived to cope with this matter.
To cope with the above-described matter, in the second embodiment, the rotation speed of the rotation roller 46a is changed to a rotation speed c that is higher than the rotation speed a and lower than the rotation speed b for a predetermined time t3 before the end of the predetermined time t2.
Consequently, it is possible to increase the rotation speed of the rotation speed b in a stepwise manner, so that it is possible to reduce a gap that occurs when the rotation speed a is increased to the rotation speed b.
The rotation speed of the rotation roller 46a is not rapidly increased, so that it is possible to reduce the possibility that the sheet surface is damaged by contact with the rotation roller 46a.
The rotation speed b, as the rotation speed after stacking for conveyance toward the rear end stopper 48 by the tapping roller 46, is generally set to an optimal value based on sheet information. In reality, a user inputs information, such as a thickness or strength of a sheet, and the rotation speed b is automatically set based on the information.
When the information is manually input, it is cumbersome to set the input, and an input error may occur. If a type of a sheet to be actually used and the input information do not match each other, a sheet surface may be damaged or an alignment failure due to a conveyance failure may occur.
The third embodiment is conceived to cope with the above-described matters.
As illustrated in
In the third embodiment, a combination of the rotation roller 46a and the supporting roller 56a corresponds to the configuration for ejecting paper by the the paper ejection roller 62 and the driven roller 64 as illustrated in
On the inner side of the endless belt 56c of the belt conveying unit 56, a reflective sheet detection sensor 70 as a sheet detecting unit that detects a sheet is arranged between the rotation roller 46a and the returning roller 50.
In a supporting portion of the returning roller 50, a deflection detecting unit 72 that detects deflection of a sheet is arranged. The deflection detecting unit 72 includes a contact, one end of which is supported and which is rotatable in a vertical direction, and includes a detection sensor that detects a rotation angle of the contact. In the third embodiment, a predetermined amount of deflection (height of deflection) of a sheet is detected.
A leading end of a first sheet 66a conveyed onto the staple tray 44 by the intermediate conveying roller pair 40 is nipped between the rotation roller 46a of the tapping roller 46 and the belt 56c, and the sheet 66a is conveyed to the paper ejection tray 60 side by the rotation roller 46a rotating clockwise.
The tapping roller 46 can be separated from the opposing supporting roller 56a, and can change a conveying force of the rotation roller 46a by changing a contact pressure of the rotation roller 46a against the supporting roller 56a.
When the sheet 66a is conveyed by a predetermined distance to the paper ejection tray 60 side by the rotation roller 46a, as illustrated in
The above-described predetermined distance is different for each sheet size, and is set to a time (distance) from when the rear end of the sheet 66a passes through the nip of the intermediate conveying roller pair 40 (a time at which the intermediate conveying sensor 42 detects the rear end) to when the rear end of the sheet 66a remains between the nip of the rotation roller 46a.
If productivity is taken into account, it is desirable to set the predetermined distance to a value close to a distance at which the rear end of the sheet 66a passes through the nip of the intermediate conveying roller pair 40.
When the sheet 66a is conveyed by the rotation roller 46a, the sheet detection sensor 70 detects the rear end of the sheet 66a (
When the deflection detecting unit 72 detects a predetermined amount of deflection, the rotation roller 46a stops and the sheet conveyance is stopped, so that the sheet can be stopped such that the position of the rear end of the sheet is accurately located at a nip position of the returning roller 50, without the influence of fluctuation in the sheet conveyance or damage on the sheet depending on each paper type, each paper, or a difference in the environment or the like (
If a detection height to be detected by the deflection detecting unit 72 is too low, error detection may occur when a large number of papers are set on the staple tray. In contrast, if the detection height is too high, paper may be damaged due to deflection. Therefore, it is desirable to set the detection height of the deflection detecting unit 72 in a range in which error detection does not occur even when a large number of papers are set and in which paper is not damaged due to deflection.
A time from when the sheet detection sensor 70 detects the rear end of the sheet to when the deflection detecting unit 72 detects occurrence of a predetermined amount of deflection on the sheet is measured (determined).
Assuming that a measured time is denoted by t and predetermined values t1 and t2 have a relationship such that t1<t2, it is determined that the sheet 66a is thin paper when a paper thickness is such that t<t1, plain paper when the paper thickness is such that t1≤t<t2, and thick paper when the paper thickness is such that t2≤t.
Subsequently, the conveying force of the rotation roller 46a with respect to the sheet conveyed to the staple tray 44 by the intermediate conveying roller pair 40 is adjusted such that the conveying force is reduced when the sheet is thin paper and increased when the sheet is thick paper, so that it becomes possible to switch to optimal control, such as control to prevent damage on the thin paper or control to prevent a sheet feed failure of the thick paper, without input of paper information from a user.
In the third embodiment, the control is switched by using the two predetermined values t1 and t2. However, the number of the predetermined values t0 for switching the control may be one or three or more.
When the deflection detecting unit 72 detects occurrence of a predetermined amount of deflection of the sheet 66a, the rotation roller 46a of the tapping roller 46 stops conveyance and is separated from the supporting roller 56a.
When the rotation roller 46a is separated, a press of one side of the deflected sheet 66a is released and the deflection is returned because of the hardness of the sheet 66a (
After the rotation roller 46a is separated, the returning roller 50 conveys the sheet 66a and causes the sheet 66a to butt against the rear end stopper 48 serving as a reference fence (
Because of the deflection generated as illustrated in
A conveying force (the rotation speed b after stacking) of the rotation roller 46a of the tapping roller 46 is adjusted to an optimal value in accordance with the paper thickness calculated for the first sheet 66a.
When the sheet 66b is conveyed by a predetermined distance by the rotation roller 46a as illustrated in
Similarly to the first sheet, when the sheet 66b is conveyed by the rotation roller 46a, the rear end of the sheet 66b butts against the nip of the returning roller 50, the rotation of which is stopped, and a rear end portion of the sheet 66b is deflected. When the deflection detecting unit 72 detects a predetermined amount of deflection, the rotation roller 46a stops and the conveyance of the sheet 66b is stopped.
The rear ends of the second and subsequent sheets to be subjected to the binding process are also accurately stopped at the nip position of the returning roller 50. Therefore, it is possible to accurately align the sheets with respect to the rear end stopper 48.
If paper, such as plain paper or thick paper, that has certain hardness and is less likely to be damaged when butted against the nip of the returning roller 50 is fed, it may be possible to increase the conveying speed (rotation speed) of the rotation roller 46a to improve the productivity.
In the third embodiment, the sheet detection sensor 70 is arranged below the stacking surface of the staple tray 44, and therefore, it is difficult to detect the rear ends of the second and subsequent sheets. In this case, the rotation speed of the rotation roller 46a is adjusted based on a detection result of the amount of deflection of the first sheet, and the rotation speed is maintained constant in a single job.
In the fourth embodiment, as illustrated in
Even for the second sheet 66b and subsequent sheet, a time from when the sheet detection sensor 74 detects the rear end of the sheet to when the deflection detecting unit 72 detects a predetermined amount of deflection is measured, and the conveying force and the conveying speed of the rotation roller 46a are optimized.
As illustrated in
If the sheet detection sensor 74 is a transmissive paper detection sensor, it is only possible to detect presence or absence of a sheet, and it is difficult to accurately detect the rear ends of the second sheet 66b and subsequent sheet. Therefore, in the fourth embodiment, a sensor, such as an ultrasonic sensor, that can detect the rear end of paper from a change in the thickness is used as the sheet detection sensor 74.
When the sheet 66a is conveyed by the rotation roller 46a, the rear end of the sheet 66a butts against the nip of the returning roller 50, the rotation of which is stopped, and a rear end portion of the sheet 66a is deflected. When the deflection detecting unit 72 detects a predetermined amount of deflection, the rotation roller 46a stops and the conveyance of the sheet 66a is stopped, so that the sheet can be stopped such that the position of the rear end of the sheet is accurately located at the nip position of the returning roller 50, without the influence of fluctuation in the sheet conveyance or damage on the sheet depending on each paper type, each paper, or a difference in the environment or the like (
A time from when the sheet detection sensor 74 detects the rear end of the sheet to when the deflection detecting unit 72 detects occurrence of a predetermined amount of deflection is measured. Assuming that a measured time of the first sheet 66a is denoted by t1, a measured time of the second sheet 66b is denoted by t2, . . . , and predetermined values s1 and s2 have a relationship such that s1<s2, it is determined that paper is thin paper when a paper thickness is such that (t1+t2+ . . . tn)/n<s1, plain paper when the paper thickness is such that s1≤(t1+t2+ . . . tn)/n<s2, and thick paper when the paper thickness is such that s2≤(t1+t2+ . . . tn)/n.
Subsequently, the conveying force of the returning roller 50 with respect to the sheet conveyed toward the rear end stopper 48 by the rotation roller 46a is adjusted such that the conveying force is reduced when the paper is thin paper and increased when the paper is thick paper, so that it becomes possible to prevent erroneous detection of the paper thickness due to sudden fluctuation in the measured time tn.
Consequently, it becomes possible to switch to optimal control, such as control to prevent damage on the thin paper or control to prevent a sheet feed failure of the thick paper, without input of paper information from a user.
Furthermore, if paper, such as plain paper or thick paper, that has certain hardness and is less likely to be damaged when butted against the nip of the returning roller 50 is fed, it may be possible to increase the conveying speed of the rotation roller 46a to improve the productivity.
In the fourth embodiment, the control is switched by using the two predetermined values s1 and s2. However, the number of the predetermined values sn for switching the control may be one or three or more. Moreover, it may be possible to use a method of determining a threshold for the value tn in each case, without using the value s.
A feature of the fifth embodiment is in that paper type information, which is determined based on a time taken to detect a predetermined amount of deflection on the staple tray 44, is used to optimize a conveying force of a returning member for stacking a sheet on the paper ejection tray 60.
As illustrated in
The sheet bundle 76 is discharged on the paper ejection tray 60 by the rotation roller 46a and the belt conveying unit 56. The conveying force of the rotation roller 46a is adjusted to an optimal value in accordance with a paper thickness calculated through deflection detection on the staple tray 44.
As illustrated in
The returning roller 80 can change the conveying force by changing a contact pressure against the paper surface, and the conveying force thereof is adjusted to an optimal value in accordance with a paper thickness calculated on the staple tray 44. For example, by reducing the conveying force in the case of thin paper and increasing the conveying force in the case of thick paper, it is possible to align sheets while maintaining the paper quality.
An operation performed after a sheet butts against the rear end stopper 48 in each of the above-described embodiments will be described below.
As illustrated in
As illustrated in
As described above, at the stage illustrated in
The moving speed of the jogger fences 52 is increased in the case of thick paper to improve the productivity, and the moving speed of the jogger fences 52 is decreased in the case of thin paper.
By doing so, it is possible to reduce damage due to the contact of the jogger fences 52 with the sheet 66a, and prevent reduction in the paper quality.
As illustrated in
A punching operation performed by the punching unit 16 will be described based on
As illustrated in
As illustrated in
A force (velocity) at the time of punching is adjusted based on information on a paper thickness obtained through the above-described deflection detection. In general, a large sound occurs when a punching force is large. However, by reducing the force with respect to thin paper for which the punching force is not needed, it is possible to reduce the sound at the time of punching.
As illustrated in
In the above-described embodiments, a change in the conveying force of the rotation roller 46a or the returning roller 50 according to the condition, such as the paper thickness, is described as a change in the rotation speed. However, this may be realized by changing a contact pressure between the rotation roller 46a or the returning roller 50 and an opposing member.
While the preferred embodiments of the present invention have been explained above, the present invention is not limited to the specific embodiments, and various modifications and changes may be made within the scope of the appended claims unless otherwise specified in this document.
The effects described in relation to the embodiments of the present invention are examples of the most preferred effects, and not limited to those described in the embodiments.
According to the embodiments of the present invention, it is possible to provide a sheet post-processing apparatus capable of stabilizing a landing state of a sheet on a stack tray, and contributing to sheet alignment accuracy and post-processing accuracy.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
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