US20090008861A1

US20090008861A1 - Sheet feeding device

Info

Publication number: US20090008861A1
Application number: US12/106,633
Authority: US
Inventors: Yuki Kasahara; Koichi Minami; Nobuhisa Yamazaki; Masaya TAKAMORI
Original assignee: PFU Ltd
Current assignee: PFU Ltd
Priority date: 2007-07-06
Filing date: 2008-04-21
Publication date: 2009-01-08
Also published as: JP2009012959A; DE102008019831A1; CN101337628A

Abstract

A sheet feeding device includes a feeding unit that feeds a sheet; a rolling member that rolls by having contact with the sheet being fed by the feeding unit; a supporting member that moves along with a behavior of the sheet with supporting the rolling member so that the rolling member rolls in a feeding direction of the sheet at a predetermined position on the sheet; an acceleration measuring unit that measures accelerations acting on the supporting member in three directions; and a detecting unit that detects a feed error of the sheet based on the accelerations measured by the acceleration measuring unit.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a sheet feeding device, and more particularly, to a sheet feeding device capable of feeding a plurality of sheets by separating the sheets one by one.
2. Description of the Related Art
A sheet feeding device is generally mounted on an apparatus that processes a plurality of sheets, for example, an image reading apparatus such as an image scanner, a copier, a facsimile machine, or a character recognition device. The sheet feeding device separates stacked sheets one by one, and sequentially feeds the separated sheet to the image reading apparatus. Even when a number of sheets are stacked, the image reading apparatus can process the sheets one by one because the sheet feeding device automatically feeds the sheets one by one to the image reading apparatus. However, in such a sheet feeding device, if a feed error occurs while a sheet is being fed, it may cause a damage to the sheet. For example, the sheet may be bent and folded due to the feed error.
A conventional sheet transporting device shown in Japanese Patent Application Laid-open No. 2007-31104 discloses a pair of vibrating members, an acceleration sensing unit, and a feed-error detecting unit. The vibrating members are arranged in a width direction of a sheet path, and respectively receive a vibration of a sheet being fed. The acceleration sensing unit senses each of the vibrations transmitted to the vibrating members. The feed-error detecting unit detects a feed error of the sheet based on the vibrations sensed by the acceleration sensing unit. If the sheet is fed properly, i.e., if the sheet is not fed askew, the acceleration sensing unit senses the vibrations transmitted to the vibrating members simultaneously, so that output signals from the acceleration sensing unit overlap each other as the peaks in the same timing. On the other hand, if the sheet is fed askew, output signals from the acceleration sensing unit form two peaks in the transport of one sheet, whereby the sheet transporting device can detect a skew of the sheet.
However, the conventional sheet transporting device needs to include a plurality of the acceleration sensing units and the vibrating members to cope with a plurality of types of feed errors occurring while a sheet is fed. Such feed errors include a so-called cumulative skew caused by a rotation or deformation of a sheet being fed and a jam caused by uplift of a sheet or the like. Therefore, there has been a need of a sheet feeding device capable of detecting a plurality of types of feed errors before a damage to a sheet occurs with a simple configuration.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to an aspect of the present invention, a sheet feeding device includes a feeding unit that feeds a sheet; a rolling member that rolls by having contact with the sheet being fed by the feeding unit; a supporting member that moves along with a behavior of the sheet with supporting the rolling member so that the rolling member rolls in a feeding direction of the sheet at a predetermined position on the sheet; an acceleration measuring unit that measures accelerations acting on the supporting member in three directions; and a detecting unit that detects a feed error of the sheet based on the accelerations measured by the acceleration measuring unit.
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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a sheet feeding device according to a first embodiment of the present invention;

FIG. 2 is a plan view of the sheet feeding device according to the first embodiment;

FIG. 3 is a side view of the sheet feeding device according to the first embodiment;

FIG. 4A is a plan view of an acceleration detecting unit according to the first embodiment;

FIG. 4B is a front view of the acceleration detecting unit according to the first embodiment;

FIG. 4C is a side view of the acceleration detecting unit according to the first embodiment;

FIG. 5 is a plan view of the sheet feeding device according to the first embodiment for explaining an operation of the acceleration detecting unit;

FIG. 6 is a side view of the sheet feeding device according to the first embodiment for explaining an operation of the acceleration detecting unit;

FIG. 7 is a flowchart of a feed-error detecting process performed by the sheet feeding device according to the first embodiment;

FIG. 8A is a plan view of an acceleration detecting unit of a sheet feeding device according to a second embodiment of the present invention;

FIG. 8B is a front view of the acceleration detecting unit according to the second embodiment;

FIG. 8C is a side view of the acceleration detecting unit according to the second embodiment;

FIG. 9 is a plan view of a sheet feeding device according to a third embodiment of the present invention;

FIG. 10 is a side view of the sheet feeding device according to the third embodiment;

FIG. 11 is a block diagram of a sheet feeding device according to a fourth embodiment of the present invention;

FIG. 12 is a perspective view of an acceleration detecting unit of the sheet feeding device according to the fourth embodiment;

FIG. 13 is a graph of an example of an acceleration waveform when no feed error occurs in the sheet feeding device according to the fourth embodiment;

FIG. 14 is a graph of an example of an acceleration waveform when a feed error occurs in the sheet feeding device according to the fourth embodiment; and

FIG. 15 is a flowchart of a feed-error detecting process performed by the sheet feeding device according to the fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawings.
A sheet feeding device 1 according to a first embodiment of the present invention is explained in detail below with reference to FIGS. 1 to 7.
FIG. 1 is a block diagram of the sheet feeding device 1. FIG. 2 is a plan view of the sheet feeding device 1. FIG. 3 is a side view of the sheet feeding device 1. The sheet feeding device 1 automatically feeds stacked sheets S as sheet-like media by separating the sheet S one by one as shown in FIGS. 1 to 3.
It is assumed that the sheet feeding device 1 is mounted on an image reading apparatus capable of processing a plurality of sheets S, such as an image scanner, a copying machine, a facsimile machine, or a character recognition device. The sheet feeding device 1 separates stacked sheets S one by one, and sequentially feeds the separated sheet S to the image reading apparatus.
The sheet feeding device 1 automatically and sequentially feeds a plurality of sizes and a massive amount of sheets S to a conveying unit (not shown) of the image reading apparatus. The sheet feeding device 1 includes a hopper 2 as a sheet stacking unit, a separate-feeding unit 3 as a feeding unit, and a control unit 4.
Incidentally, a direction of which a sheet S is fed by the sheet feeding device 1 is referred to as a “feeding direction Y”, a direction horizontally-perpendicular to the feeding direction Y is referred to as a “width direction X”, and a direction perpendicular to both the feeding direction Y and the width direction X is referred to as a “height direction Z”.
The separate-feeding unit 3 automatically and sequentially feeds sheets S stacked on the hopper 2 by separating the sheet S one by one. The conveying unit of the image reading apparatus is located on the downstream side of the separate-feeding unit 3 in the feeding direction Y.
The conveying unit is included in the image reading apparatus on which the sheet feeding device 1 is mounted, and conveys a sheet S fed from the sheet feeding device 1 to any of units included in the image reading apparatus. For example, an optical unit as an image reading unit is provided on a sheet conveying path of the conveying unit. While a sheet S is conveyed on the sheet conveying path by the conveying unit, the optical unit reads out an image on the sheet S. The conveying unit includes, for example, a drive roller (not shown) and a driven roller (not shown). The drive roller is driven to rotate around a central axis as a rotating shaft by a drive force from a drive source (not shown). By a rotation transmission from the drive roller, the driven roller rotates around a central axis as a rotating shaft in accordance with the rotation of the drive roller. The drive roller and the driven roller are arranged to be opposed to each other along the width direction X. The driven roller is pressed (or biased) towards the drive roller by a biasing unit (not shown) to have contact with the drive roller. With the bias applied to the driven roller, a sheet S is sandwiched between an outer circumferential surface of the drive roller and an outer circumferential surface of the driven roller. A plurality of such drive rollers (not shown) and a plurality of such driven rollers (not shown) are provided along the sheet conveying path. As the drive rollers are driven to rotate, the sheet S is passed between the drive rollers and the driven rollers sequentially, and conveyed to any of the units in the image reading apparatus, for example, the optical unit.
The hopper 2 has a substantially rectangular stacking surface 21. A plurality of sheets S is stacked on the stacking surface 21. The stacked sheets S are pressed towards the stacking surface 21 by a biasing unit (not shown). The hopper 2 includes a hopper lifting mechanism (not shown) so that the hopper 2 is lifted up and down in the height direction Z depending on the quantity of sheets S stacked on the stacking surface 21.
The separate-feeding unit 3 employs an uppermost-sheet feeding method. The separate-feeding unit 3 includes a separation roller 31 and a brake roller 32. The separation roller 31, as a separating unit, separates a sheet S placed on the top of the sheets S stacked on the stacking surface 21 (hereinafter, “the top sheet S”) from the sheets S and feeds the sheets S one by one. The brake roller 32 constrains the sheets S other than the top sheet S having direct contact with the separation roller 31 not to be fed along with the top or uppermost sheet S.
The separation roller 31 is made of a material with a large frictional force (or high coefficient of friction) such as a foamed rubber, and has a cylindrical shape. A central axis of the separation roller 31 is set up to be parallel to the width direction X, i.e., in a direction perpendicular to the feeding direction Y along the stacking surface 21. In addition, the separation roller 31 is set up in such a way that the central axis of the separation roller 31 is located above an upper surface of the hopper 2 (above the stacking surface 21), and a predetermined distance is kept between an outer circumferential surface of the separation roller 31 and the stacking surface 21 in the height direction Z. The hopper 2 is set up in such a way that sheets S are stacked on the stacking surface 21 so that trailing edges (edges on the upstream side in the feeding direction Y) of the sheets S are located on the upstream side of the separation roller 31 in the feeding direction Y. As the hopper 2 is lifted up in the height direction Z, the hopper 2 and the separation roller 31 get closer to each other. As the hopper 2 is lifted down in the height direction Z, the hopper 2 and the separation roller 31 get further away from each other.
The separation roller 31 is connected to a drive motor 31 a as a driving unit via a transmission gear (not shown) and a belt (not shown). The separation roller 31 is driven to rotate around the central axis as a rotating shaft by the application of a rotation drive force from the drive motor 31 a. The separation roller 31 is driven to rotate in a pick direction, i.e., a direction of which the outer circumferential surface of the separation roller 31 rolls to the downstream side in the feeding direction Y on the stacking surface 21.
The brake roller 32 has a cylindrical shape with the almost same length as that of the separation roller 31. In the same manner as the separation roller 31, a central axis of the brake roller 32 is set up to be horizontally perpendicular to the feeding direction Y, i.e., along the width direction X. The brake roller 32 rotates around the central axis as a rotating shaft. The brake roller 32 is arranged to be opposed to the separation roller 31. The central axis of the brake roller 32 is set up to be located between the central axis of the separation roller 31 and the stacking surface 21 in the height direction Z. The brake roller 32 is pressed (or biased) towards the separation roller 31 by a biasing unit (not shown) to have contact with the separation roller 31. By a rotation transmission from the separation roller 31, the brake roller 32 rotates around the central axis as a rotating shaft in accordance with the rotation of the separation roller 31 in such a direction that an outer circumferential surface of the brake roller 32 rolls to the downstream side in the feeding direction Y at a contact portion where the brake roller 32 has contact with the separation roller 31. In the first embodiment, the brake roller 32 is biased towards the separation roller 31 by the biasing unit. Alternatively, the brake roller 32 can be driven to rotate in a direction opposite to the rotating direction of the separation roller 31 instead of providing the biasing unit.
The control unit 4 includes a microcomputer, and controls the sheet feeding device 1. The control unit 4 is connected to the drive motor 31 a, and further electrically connected to an empty sensor (not shown), a sheet sensor (not shown), and the like. The empty sensor is used to detect whether there is any sheet S which trailing edge is located on the upstream side of the separation roller 31 on the stacking surface 21. The sheet sensor is used to detect the quantity of sheets S stacked on the stacking surface 21. As the empty sensor and the sheet sensor, for example, a photo sensor using an infrared radiation or the like can be used. The empty sensor and the sheet sensor respectively transmit a sensed signal indicating a result of the detection to the control unit 4.
In the sheet feeding device 1, the separation roller 31 is driven to rotate in the pick direction, so that the top sheet S can be picked up from sheets S stacked on the stacking surface 21 located on the upstream side of the separation roller 31 on the outer circumferential surface of the separation roller 31, and fed to the downstream side in the feeding direction Y (to the side of the conveying unit of the image reading apparatus). When the top sheet S is fed by the separation roller 31, it may happen that a sheet S other than the top sheet S (for example, a sheet S located beneath the top sheet S) is also fed to the downstream side in the feeding direction Y along with the top sheet S due to a frictional force generated between the sheets S. However, in the sheet feeding device 1, the sheet S fed along with the top sheet S can be separated from the top sheet S by the brake roller 32.
Namely, while a leading edge of the top sheet S is held between the separation roller 31 and the brake roller 32, the sheet S fed along with the top sheet S is constrained not to be fed to the downstream side in the feeding direction Y by having contact with the brake roller 32, i.e., the sheet S fed along with the top sheet S is stopped at the upstream side of the brake roller 32. After the top sheet S is fed to the downstream side in accordance with the rotation of the separation roller 31, a leading edge of the sheet S stopped at the upstream side of the brake roller 32 is subsequently held between the separation roller 31 and the brake roller 32, and then fed to the downstream side in accordance with the rotation of the separation roller 31. The hopper 2 is lifted up in the height direction Z depending on the quantity of sheets S stacked on the stacking surface 21. In this manner, the sheet S fed along with the top sheet S is separated from the top sheet S by the separation roller 31 and the brake roller 32, and only the top sheet S is fed to the conveying unit one by one sequentially. This means the uppermost-sheet feeding method.
When a feed error occurs while a sheet S is fed, it may cause a damage to the sheet S, for example, the sheet may be bent and folded.
To cope with the problems, the sheet feeding device 1 is configured to detect a feed error of a sheet S based on accelerations acting on a roller supporting mechanism in three directions (or dimensions). Therefore, the sheet feeding device 1 can detect a plurality of types of feed errors before any damage to a sheet S occurs with a simple configuration. Incidentally, a detection of a feed error by the sheet feeding device 1 also includes a forecast of a feed error before the feed error occurs, so that it is possible to prevent a sheet S from a damage due to the feed error.
Specifically, the sheet feeding device 1 further includes an acceleration detecting unit 5 as shown in FIGS. 1 to 3. Moreover, the control unit 4 includes a processing unit 41, a storing unit 42, and an input/output unit 43. The acceleration detecting unit 5 includes a following roller 6, a roller supporting mechanism 7, and a three-axis accelerometer 8. The following roller 6 rolls by having contact with a sheet S being fed. The roller supporting mechanism 7 supports the following roller 6, and is capable of moving and rotating along with a behavior of the sheet S together with the following roller 6. The three-axis accelerometer 8 measures an acceleration acting on the roller supporting mechanism 7.
The following roller 6 has a cylindrical shape, and a rotating shaft of the following roller 6 is arranged along the width direction X. The following roller 6 is arranged at the almost same level of the separation roller 31 in the height direction Z and on the upstream side of the separation roller 31 in the feeding direction Y. When the top sheet S is fed by the separate-feeding unit 3, the following roller 6 rolls by having line contact with the top sheet S on a line along the width direction X at the upstream side of the separate-feeding unit 3. The following roller 6, the separation roller 31, and the brake roller 32 are arranged on a center line of the properly-fed sheet S in the width direction X. In addition, the rotating shafts of the following roller 6, the separation roller 31, and the brake roller 32 are arranged substantially parallel to one another.
FIGS. 4A to 4C are respectively a plan view, a front view, and a side view of the acceleration detecting unit 5. As shown in FIGS. 4A to 4C, the roller supporting mechanism 7 rotatably supports the following roller 6 so that the following roller 6 can roll in the feeding direction Y at a predetermined position. The roller supporting mechanism 7 can move in the height direction Z and rotate around an axis along the height direction Z along with a behavior of the sheet S, at least. The roller supporting mechanism 7 includes a roller support shaft 71, a bracket 72, a pair of roller supporting members 73, a roller-side coupling member 74, and a supporting-member-side coupling member 75.
The roller support shaft 71 is arranged along the width direction X, and serves as the rotating shaft of the following roller 6. The bracket 72 has a concave portion opened downward (to the side of the sheet S). Both ends of the roller support shaft 71 are fixed on an inner surface of the concave portion. The rotating shaft of the following roller 6 is rotatably supported by the bracket 72 via the roller support shaft 71. The roller-side coupling member 74 is arranged on an upper outer surface of the concave portion (on a surface opposite to the side of the sheet S). The roller-side coupling member 74 includes a pair of coupling plates 74 a and 74 b. The coupling plates 74 a and 74 b are arranged in such a way that a side surface of each of the coupling plates 74 a and 74 b is faced to each other on the upper outer surface of the bracket 72, and extend along the width direction X to be opposed to each other. The coupling plate 74 a is located on the downstream side, and the coupling plate 74 b is located on the upstream side in the feeding direction Y.
The roller supporting members 73 are arranged to be parallel to each other in the feeding direction Y with keeping a predetermined distance in the width direction X between the roller supporting members 73. The roller supporting members 73 respectively include, for example, a member with a certain elastic force such as a plate spring so as to return the following roller 6 back to an initial position. Each of the roller supporting members 73 includes a base-end support shaft 76 at its base end portion located on the upstream side in the feeding direction Y and a leading-end support shaft 77 at its leading end portion located on the downstream side in the feeding direction Y. The base-end support shaft 76 and the leading-end support shaft 77 are arranged to be parallel to each other in the width direction X. The supporting-member-side coupling member 75 is rotatably attached to the leading end portion of each of the roller supporting members 73 via the leading-end support shaft 77. The supporting-member-side coupling member 75 and the roller-side coupling member 74 are rotatably coupled to each other via a feeding-directional shaft 78 so that the supporting-member-side coupling member 75 and the roller-side coupling member 74 can rotate respectively. The feeding-directional shaft 78 is arranged to be parallel to the feeding direction Y. The feeding-directional shaft 78 and the supporting-member-side coupling member 75 are arranged between the coupling plates 74 a and 74 b in the feeding direction Y. The base end portion of each of the roller supporting members 73 is supported by a casing (not shown) of the sheet feeding device 1 via the base-end support shaft 76.
The entire roller supporting mechanism 7 can rotate around the base-end support shaft 76, i.e., around an axis in the width direction X together with the following roller 6. In addition, the entire roller supporting mechanism 7 can also rotate around the base end portion in the height direction Z together with the following roller 6 by the action of a reaction force to the elastic force of the roller supporting members 73. At this time, the following roller 6 supported by the bracket 72 can roll around the roller support shaft 71, and also the bracket 72 can rotate around the feeding-directional shaft 78, i.e., around an axis in the feeding direction Y together with the following roller 6. Therefore, the roller supporting mechanism 7 can move along with a behavior of the sheet S fed by the separate-feeding unit 3 with supporting the following roller 6 so that the following roller 6 rolls in the feeding direction Y at the predetermined position. In other words, when there is any change in a behavior of the sheet S fed by the separate-feeding unit 3, the following roller 6 and the roller supporting mechanism 7 can move (rotate) along with the behavior of the sheet S.
As the three-axis accelerometer 8, any types of accelerometers, such as an electrostatic capacitive accelerometer and a piezoelectric accelerometer, can be used. In the first embodiment, a complete three-axis accelerometer manufactured by Analog Devices Inc. is used as the three-axis accelerometer 8. The three-axis accelerometer 8 can measure not only a static acceleration such as a gravity but also a dynamic acceleration such as a movement, impact, and vibration. The three-axis accelerometer 8 can measure an acceleration acting on the three-axis accelerometer 8 itself, and capture a gravity as the acceleration, and also detect a tilt of an object on which the three-axis accelerometer 8 is mounted. The three-axis accelerometer 8 can measure an acceleration, for example, in the range of 1 G to 3 G.
The three-axis accelerometer 8 is provided on the coupling plate 74 a, and simultaneously measures accelerations Gx, Gy, and Gz that act on the roller supporting mechanism 7 in the width direction X, the feeding direction Y, and the height direction Z, respectively. A sampling interval (an interval between data acquisitions) of each of the accelerations Gx, Gy, and Gz measured by the three-axis accelerometer 8 is set up to a relatively short interval but a sufficient interval to cope with a moving (rotating) speed of the following roller 6 and the roller supporting mechanism 7 for moving (rotating) along with the sheet S, i.e., a time to get the following roller 6 and the roller supporting mechanism 7 to move (rotate) along with the sheet S in accordance with a change in a behavior of the sheet S being fed. The sampling interval is set up to, for example, about 0.1 second to 0.25 second. When there is any change in the behavior of the sheet S being fed by the separate-feeding unit 3, the three-axis accelerometer 8 can reliably measure an acceleration acting on the following roller 6 and the roller supporting mechanism 7, which move (rotate) along with the behavior of the sheet S, by dividing the acceleration into three components of accelerations in three directions, i.e., accelerations Gx, Gy, and Gz. In other words, by sensing behaviors of the following roller 6 and the roller supporting mechanism 7, the three-axis accelerometer 8 can indirectly sense a behavior of the sheet S via the following roller 6 and the roller supporting mechanism 7. The three-axis accelerometer 8 is electrically connected to the control unit 4, and outputs the measured accelerations Gx, Gy, and Gz to the control unit 4.
The control unit 4 includes a computer such as a personal computer. As shown in FIG. 1, in the control unit 4, the processing unit 41 and the storing unit 42 are connected to each other. Furthermore, the drive motor 31 a and the three-axis accelerometer 8 are connected to the processing unit 41 via the input/output unit 43.
The storing unit 42 stores therein a computer software program executing a feed-error detecting process performed by the sheet feeding device 1. The storing unit 42 is composed of any of a hard disk drive, a magneto-optical disk device, a nonvolatile memory (a read-only memory medium) such as a compact disk read-only memory (CD-ROM) or a flash memory, and a volatile memory such as a random access memory (RAM) either alone or in combination.
The computer software program can be combined with other computer software program, which is stored in a computer system in advance, so as to perform the feed-error detecting method. Alternatively, the computer software program capable of exercising a function of the processing unit 41 can be stored in a computer-readable recording medium so that the computer system can read the computer software program from the recording medium to execute a feed-error detecting process with the feed-error detecting method. Incidentally, it is assumed that the “computer system” includes an operating system (OS) and hardware such as a peripheral device. The storing unit 42 can be either built in the processing unit 41 or included in other devices (for example, a database server).
The processing unit 41 includes a memory (not shown) and a central processing unit (CPU) (not shown). When the feed-error detecting process is executed, the processing unit 41 calculates a value by reading the computer software program into the memory in accordance with predetermined procedures of the feed-error detecting method. At this time, the processing unit 41 arbitrarily stores the calculated value obtained in midstream of the calculation in the storing unit 42, and keeps performing the calculation with the value fetched out from the storing unit 42. Alternatively, such a function of the processing unit 41 can be exercised with a dedicated hardware instead of the computer software program.
As shown in FIG. 1, the processing unit 41 includes an error detecting unit 44, a counting unit 45, and a feeding stop unit 46.
The error detecting unit 44 detects a feed error of the sheet S based on accelerations Gx, Gy, and Gz measured by the three-axis accelerometer 8. When an increase or decrease of any of the accelerations Gy and Gx is continued for a predetermined time period, the error detecting unit 44 detects a skew (a cumulative skew) of the sheet S as a feed error of the sheet S.
For example, as shown in FIG. 2, when the sheet S is fed properly by the separate-feeding unit 3, the following roller 6 supported by the roller supporting mechanism 7 rolls with having contact with the sheet S being properly fed in the feeding direction Y at the same position in an idling manner. Namely, although the sheet S is fed in the feeding direction Y, the following roller 6 is supported by the roller supporting mechanism 7 at the predetermined position, so that the following roller 6 rolls in the idling manner at the predetermined position. At this time, although the following roller 6 rolls, the three-axis accelerometer 8 does not rotate because the three-axis accelerometer 8 is provided not directly to the following roller 6 but to the roller supporting mechanism 7. Therefore, no acceleration acts on the three-axis accelerometer 8 in any direction, so that the three-axis accelerometer 8 senses no change in each of the accelerations Gx, Gy, and Gz. In other words, the accelerations Gx, Gy, and Gz are all zero.
On the other hand, for example, as shown in FIG. 5, when the sheet S is skewed while the sheet S is being fed by the separate-feeding unit 3, there is a change in a behavior of the sheet S due to an occurrence of a cumulative skew of the sheet S. A moment of rotation around an axis in the height direction Z acts on the following roller 6 having line contact with the sheet S on a line along the width direction X and the roller supporting mechanism 7 supporting the following roller 6. The moment of rotation acts as a reaction force to the elastic force of the roller supporting members 73, so that the roller supporting mechanism 7 rotates around the base end portions of the roller supporting members 73 in the height direction Z along with the behavior of the sheet S together with the following roller 6. At this time, the three-axis accelerometer 8 measures an acceleration acting on the three-axis accelerometer 8 in accordance with the rotation around the axis in the height direction Z by dividing the acceleration into accelerations Gx and Gy as components of accelerations in the width direction X and the feeding direction Y. The error detecting unit 44 can detect a skew (a cumulative skew) of the sheet S as a feed error of the sheet S based on either one or both of the accelerations Gx and Gy.
When an increase or decrease of an acceleration Gz is continued for a predetermined time period, the error detecting unit 44 detects a jam as a feed error of the sheet S. In this case, the detection of a jam by the error detecting unit 44 indicates that the error detecting unit 44 forecasts an occurrence of a jam before the jam occurs so as to prevent a damage to the sheet S from occurring. For example, as shown in FIG. 6, when the sheet S is lifted up while the sheet S is being fed by the separate-feeding unit 3, there is a change in a behavior of the sheet S due to an occurrence of a jam caused by the uplift of the sheet S. A force generated by the uplift of the sheet S acts on the following roller 6 having contact with the sheet S and the roller supporting mechanism 7 supporting the following roller 6. By the action of the force, the roller supporting mechanism 7 rotates around the base-end support shaft 76, i.e., around the axis in the width direction X together with the following roller 6 along with the behavior of the sheet S. At this time, the three-axis accelerometer 8 measures an acceleration acting on the three-axis accelerometer 8 in accordance with the rotation around the base-end support shaft 76 (the axis in the width direction X) by dividing the acceleration into accelerations Gy and Gz as components of accelerations in the feeding direction Y and the height direction Z. The error detecting unit 44 can forecast an occurrence of a jam before the jam occurs as a feed error of the sheet S based on the acceleration Gz.
In this manner, with only one sensor, i.e., the three-axis accelerometer 8, behaviors of the following roller 6 and the roller supporting mechanism 7 can be sensed, and thereby sensing a behavior of the sheet S indirectly. Therefore, the sheet feeding device 1 can detect a plurality of types of feed errors separately with a compact and simple configuration.
Incidentally, the error detecting unit 44 is configured to detect a skew or forecast an occurrence of a jam only when an increase or decrease of an acceleration sensed by the three-axis accelerometer 8 is continued for the predetermined time period. This is to prevent the error detecting unit 44 from detecting a skew or forecasting an occurrence of a jam by mistake. In other words, a feed error is detected based on not a momentary measurement value of an acceleration measured by the three-axis accelerometer 8 but an amount of temporal change in the acceleration for the predetermined time period. Therefore, it is possible to eliminate the effect of noise, and thereby preventing a false detection. In addition, it is possible to grasp a status of a feed error in more detail. The predetermined time period can be arbitrarily set up depending on the sensitivity of detection of a skew or forecast of an occurrence of a jam.
Furthermore, the reason why the error detecting unit 44 is configured to detect a skew or forecast an occurrence of a jam only when an increase or decrease of an acceleration sensed by the three-axis accelerometer 8 is continued for the predetermined time period is that a measurement value of the acceleration output from the three-axis accelerometer 8 varies either positive or negative oppositely depending on a direction of action of the acceleration. For example, a measurement value of the acceleration varies either positive or negative oppositely depending on whether an acceleration in the width direction X acts on the left or right side toward the downstream side in the feeding direction Y. Therefore, when an increase or decrease of an acceleration is continued, it indicates that the acceleration, for example, in the width direction X continuously acts on either side. Unless otherwise noted, a case where a skew or a jam is detected by a continuous increase of an acceleration is explained below. Although an explanation about a case of a continuous decrease of an acceleration is omitted, a skew or a jam can be detected by a continuous decrease of an acceleration in about the same manner as the case of the continuous increase.
When an increase or decrease of each of components of accelerations in the width direction X, the feeding direction Y, and the height direction Z is continued based on accelerations Gx, Gy, and Gz measured by the three-axis accelerometer 8, i.e., when a previously-measured acceleration increases and a currently-measured acceleration also increases or the previously-measured acceleration decreases and the currently-measured acceleration also decreases, the counting unit 45 increments a value of a counter for the acceleration by one. When the value reaches or exceeds a threshold, i.e., when the increase or decrease of the acceleration is continued for the predetermined time period, the error detecting unit 44 detects a skew or a jam. The feeding stop unit 46 stops the feeding of the sheet S by the separate-feeding unit 3 depending on a result of the detection by the error detecting unit 44. If the feeding of the sheet S is continued even though a skew or a jam is detected, it may cause a damage to the sheet S. Therefore, when the error detecting unit 44 detects a feed error of the sheet S, the feeding stop unit 46 controls the drive motor 31 a to stop driving the separation roller 31 so that the feeding of the sheet S is stopped. Consequently, it is possible to prevent a damage to the sheet S from occurring.
A feed-error detecting process performed by the sheet feeding device 1 is explained in detail below with reference to a flowchart shown in FIG. 7. The control unit 4 determines whether a sheet S is being fed at this moment (Step S100). If the sheet S is not being fed at this moment (NO at Step S100), the counting unit 45 clears all values of each of counters for accelerations in each direction, and the feed-error detecting process is terminated as a normal end. If the sheet S is being fed at this moment (YES at Step S100), the control unit 4 acquires accelerations Gx, Gy, and Gz respectively in the width direction X, the feeding direction Y, and the height direction Z that are measured at predetermined sampling intervals by the three-axis accelerometer 8 (Step S102), and stores the acquired accelerations Gx, Gy, and Gz in a time trace buffer (not shown) of the storing unit 42 (Step S104).
The control unit 4 compares the currently-acquired accelerations Gx, Gy, and Gz with previously-acquired accelerations Gx, Gy, and Gz (Step S106), and the counting unit 45 determines whether the currently-acquired acceleration Gz increases (or decreases) as compared with the previously-acquired acceleration Gz (Step S108). If it is determined that the acceleration Gz increases (or decreases) (YES at Step S108), the counting unit 45 increments a value of a counter for the acceleration Gz by one. The error detecting unit 44 determines whether the increase (or decrease) of the acceleration Gz is continued for the predetermined time period based on whether the incremented value of the counter for the acceleration Gz reaches or exceeds a threshold (Step S110). If the error detecting unit 44 determines that the increase (or decrease) of the acceleration Gz is continued for the predetermined time period (YES at Step S110), and forecasts an occurrence of a jam caused by uplift of the sheet S, as error processes, the control unit 4 informs a user of an error, and the feeding stop unit 46 stops the feeding of the sheet S (Step S112). Then, the feed-error detecting process is terminated as an abnormal end.
If it is determined that the acceleration Gz does not increase (or decrease) (NO at Step S108), or if it is determined that the increase (or decrease) of the acceleration Gz is not continued for the predetermined time period (NO at Step S110), the counting unit 45 determines whether the currently-acquired acceleration Gy increases (or decreases) as compared with the previously-acquired acceleration Gy (Step S114). If it is determined that the acceleration Gy increases (or decreases) (YES at Step S114), the counting unit 45 increments a value of a counter for the acceleration Gy by one. The error detecting unit 44 determines whether the increase (or decrease) of the acceleration Gy is continued for the predetermined time period based on whether the incremented value of the counter for the acceleration Gy reaches or exceeds a threshold (Step S116). If the error detecting unit 44 determines that the increase (or decrease) of the acceleration Gy is continued for the predetermined time period (YES at Step S116), and detects a skew of the sheet S, as error processes, the control unit 4 informs a user of an error, and the feeding stop unit 46 stops the feeding of the sheet S (Step S118). Then, the feed-error detecting process is terminated as the abnormal end.
If it is determined that the acceleration Gy does not increase (or decrease) (NO at Step S114), or it is determined that the increase (or decrease) of the acceleration Gy is not continued for the predetermined time period (NO at Step S116), the counting unit 45 determines whether the currently-acquired acceleration Gx increases (or decreases) as compared with the previously-acquired acceleration Gx (Step S120). If it is determined that the acceleration Gx increases (or decreases) (YES at Step S120), the counting unit 45 increments a value of a counter for the acceleration Gx by one. The error detecting unit 44 determines whether the increase (or decrease) of the acceleration Gx is continued for the predetermined time period based on whether the incremented value of the counter for the acceleration Gx reaches or exceeds a threshold (Step S122). If the error detecting unit 44 determines that the increase (or decrease) of the acceleration Gx is continued for the predetermined time period (YES at Step S122), and detects a skew of the sheet S, as error processes, the control unit 4 informs a user of an error, and the feeding stop unit 46 stops the feeding of the sheet S (Step S124). Then, the feed-error detecting process is terminated as the abnormal end. If it is determined that the acceleration Gx does not increase (or decrease) (NO at Step S120), or it is determined that the increase (or decrease) of the acceleration Gx is not continued for the predetermined time period (NO at Step S122), the process control returns to Step S100.
In this manner, the sheet feeding device 1 includes the following roller 6 capable of rolling by having line contact with a sheet S fed by the separate-feeding unit 3 on a line along the width direction X of the sheet S, the roller supporting mechanism 7 that supports the following roller 6 so that the following roller 6 can roll in the feeding direction Y at the predetermined position on the sheet S, and is capable of moving and rotating along with a behavior of the sheet S fed by the separate-feeding unit 3 together with the following roller 6, the three-axis accelerometer 8 capable of measuring accelerations in three directions acting on the roller supporting mechanism 7, and the error detecting unit 44 that detects a feed error of the sheet S based on the accelerations measured by the three-axis accelerometer 8.
Specifically, the error detecting unit 44 detects a feed error of the sheet S based on accelerations Gx, Gy, and Gz in the width direction X, the feeding direction Y, and the height direction Z, respectively, which act on the roller supporting mechanism 7 capable of moving and rotating along with a behavior of the sheet S together with the following roller 6. In this manner, with only one sensor, i.e., the three-axis accelerometer 8, behaviors of the following roller 6 and the roller supporting mechanism 7 can be sensed, and thereby sensing a behavior of the sheet S indirectly. Therefore, the sheet feeding device 1 can detect a plurality of types of feed errors separately with a compact and simple configuration.
Furthermore, the three-axis accelerometer 8 can measure accelerations in the feeding direction Y, the width direction X horizontally-perpendicular to the feeding direction Y, and the height direction Z perpendicular to both the feeding direction Y and the width direction X. The roller supporting mechanism 7 can move in the height direction Z, and rotate around an axis in the height direction Z along with a behavior of the sheet S. Therefore, when there is any change in the behavior of the sheet S due to an occurrence of a cumulative skew of the sheet S, and a moment of rotation around the axis in the height direction Z acts on the following roller 6 and the roller supporting mechanism 7, the roller supporting mechanism 7 rotates around the axis in the height direction Z together with the following roller 6. At this time, the three-axis accelerometer 8 measures an acceleration acting on the three-axis accelerometer 8 in accordance with the rotation around the axis the height direction Z by dividing the acceleration into accelerations Gx and Gy in the width direction X and the feeding direction Y, respectively. Therefore, a skew of the sheet S as a feed error of the sheet S can be detected based on the accelerations Gx and Gy. When there is any change in the behavior of the sheet S due to an occurrence of a jam caused by uplift of the sheet S, and a force generated by the uplift of the sheet S acts on the following roller 6 and the roller supporting mechanism 7, the roller supporting mechanism 7 moves in the height direction Z along with the behavior of the sheet S together with the following roller 6. At this time, the three-axis accelerometer 8 measures an acceleration acting on the three-axis accelerometer 8 in accordance with the movement in the height direction Z by dividing the acceleration into accelerations Gy and Gz in the feeding direction Y and the height direction Z, respectively. Therefore, an occurrence of a jam as a feed error of the sheet S can be forecasted before the jam occurs based on the acceleration Gz.
Moreover, when an increase or decrease of any of accelerations Gy and Gx respectively in the feeding direction Y and the width direction X is continued for the predetermined time period, the error detecting unit 44 detects a skew of the sheet S as a feed error of the sheet S. Therefore, it is possible to eliminate the effect of noise, and thereby preventing a false detection of the skew.
Furthermore, when an increase or decrease of an acceleration Gz in the height direction Z is continued for the predetermined time period, the error detecting unit 44 forecasts an occurrence of a jam as a feed error of the sheet S. Therefore, it is possible to eliminate the effect of noise, and thereby preventing a false forecast of the jam.
Moreover, the following roller 6 has a cylindrical shape, and a rotating shaft of the following roller 6 is arranged along the width direction X. Therefore, when a sheet S is fed by the separate-feeding unit 3, the following roller 6 can roll by having line contact with the sheet S on a line along the width direction X.
Furthermore, the sheet feeding device 1 further includes the hopper 2 on which sheet S are stacked, and the separation roller 31 separates the sheet S stacked on the hopper 2 one by one to feed the separated sheet S sequentially. The following roller 6 is arranged on the upstream side of the separation roller 31 in the feeding direction Y. Therefore, an acceleration acting on the following roller 6 and the roller supporting mechanism 7, which move along with a behavior of the sheet S, can be measured at an appropriate position where a change in the behavior of the sheet S appears mostly. Consequently, it is possible to detect a feed error of the sheet S more reliably.
Moreover, the feeding stop unit 46 stops the feeding of the sheet S by the separate-feeding unit 3 depending on a result of the detection by the error detecting unit 44. In other words, when the error detecting unit 44 detects a feed error of the sheet S, the feeding stop unit 46 stops the feeding of the sheet S by the separate-feeding unit 3. Therefore, it is possible to prevent a damage to the sheet S from occurring.
In the first embodiment, the sheet feeding device 1 is applied to the image reading apparatus; however, the sheet feeding device 1 can be applied to any other apparatuses.
Furthermore, in the first embodiment, the following roller 6 that has a cylindrical shape and rolls by having line contact with a sheet S on a line along the width direction X is used. As long as it is possible to rotate around an axis in the height direction Z by the action of a moment of rotation around the axis in the height direction Z, any shape of a rotating body can be used instead of the following roller 6. For example, a pair of disks which rotation axes are connected to each other can be used. In this case, the disks respectively have point contact with the sheet S at a plurality of points (two points) along the width direction X.
Moreover, the following roller 6 is arranged on the downstream side of a downstream-side edge (a leading edge) of each of sheets S stacked on the stacking surface 21 in the feeding direction Y. Therefore, it is also possible to detect a so-called a leading-edge skew occurring in such a case that a sheet S is set up askew from the beginning. In this case, when the feeding of the sheet S set up askew from the beginning is started, there is a time lag in a timing of contact with the sheet S among portions of the following roller 6, i.e., the following roller 6 supposed to have line contact with the sheet S on a line along the width direction X has contact with the sheet S at a different timing depending on portions of the following roller 6. Due to a difference in a frictional force generated between the following roller 6 and the sheet S depending on portions of the following roller 6 along the width direction X, a moment of rotation around an axis in the height direction Z acts on the following roller 6, so that the following roller 6 rolls around the axis in the height direction Z. Therefore, the error detecting unit 44 can detect a leading-edge skew based on an acceleration acting on the three-axis accelerometer 8. In other words, it is also possible to detect a leading-edge skew with the three-axis accelerometer 8.
Furthermore, in the first embodiment, the error detecting unit 44 detects a skew or a jam when an increase or decrease of an acceleration sensed by the three-axis accelerometer 8 is continued for the predetermined time period. Alternatively, a threshold with respect to an acceleration sensed by the three-axis accelerometer 8 can be set up so that the error detecting unit 44 simply detects a skew or a jam when the acceleration exceeds the threshold.
Moreover, the error detecting unit 44 can detect a status of a feed error of the sheet S in detail based on a combination of accelerations Gx, Gy, and Gz in three directions measured by the three-axis accelerometer 8. In addition, a status of a feed error of the sheet S can be detected in more detail based on a temporal change in each of the accelerations Gx, Gy, and Gz. Furthermore, in the first embodiment, the feeding stop unit 46 stops the feeding of the sheet S when the error detecting unit 44 detects a feed error of the sheet S. Alternatively, depending on a more-detailed status of a feed error of the sheet S, an error process can be arbitrarily set up.
FIGS. 8A to 8C are respectively a plan view, a front view, and a side view of an acceleration detecting unit 205 of a sheet feeding device 201 according to a second embodiment of the present invention. The portions or components identical to those for the first embodiment are denoted with the same reference numerals, and the detailed description of those portions or components will not be repeated here. A difference between the sheet feeding devices 1 and 201 is that the sheet feeding device 201 includes the acceleration detecting unit 205 instead of the acceleration detecting unit 5.
The acceleration detecting unit 205 includes the following roller 6, a roller supporting mechanism 207, and the three-axis accelerometer 8. The following roller 6 rolls by having contact with a sheet S being fed. The roller supporting mechanism 207 supports the following roller 6. The three-axis accelerometer 8 measures an acceleration acting on the roller supporting mechanism 207.
The roller supporting mechanism 207 rotatably supports the following roller 6 so that the following roller 6 can roll in the feeding direction Y at a predetermined position. The roller supporting mechanism 207 can move in the height direction Z and rotate around an axis along the height direction Z along with a behavior of the sheet S, at least. The roller supporting mechanism 207 includes the roller support shaft 71, the bracket 72, a roller supporting member 273, the roller-side coupling member 74, and a supporting-member-side coupling member 275.
The roller supporting member 273 includes a support plate 273 a and a guide shaft 273 b. The support plate 273 a is fixed to, for example, a casing (not shown) of the sheet feeding device 201. The guide shaft 273 b has a rod-like shape. A base end of the guide shaft 273 b is fixed to the support plate 273 a so that the guide shaft 273 b extends downward from the support plate 273 a in the height direction Z. The supporting-member-side coupling member 275 has a guide hole 275 a extending in the height direction Z. A leading end of the guide shaft 273 b is inserted into the guide hole 275 a. The supporting-member-side coupling member 275 can move in the height direction Z with being guided by the guide shaft 273 b. The supporting-member-side coupling member 275 and the roller-side coupling member 74 are rotatably coupled to each other via the feeding-directional shaft 78.
Therefore, the roller supporting mechanism 207 can move up and down in the height direction Z along the guide shaft 273 b together with the following roller 6. When there is a change in a behavior of the sheet S due to uplift of the sheet S, and a force generated by the uplift of the sheet S acts on the following roller 6 and the roller supporting mechanism 207, the roller supporting mechanism 207 moves in the height direction Z along with the behavior of the sheet S together with the following roller 6. When there is a change in a behavior of the sheet S due to an occurrence of a cumulative skew of the sheet S, and a moment of rotation around an axis in the height direction Z acts on the following roller 6 and the roller supporting mechanism 207, the roller supporting mechanism 207 rotates around the guide shaft 273 b as a rotating shaft together with the following roller 6.
In this manner, the sheet feeding device 201 includes the following roller 6 capable of rolling by having line contact with a sheet S fed by the separate-feeding unit 3 on a line along the width direction X of the sheet S, the roller supporting mechanism 207 that supports the following roller 6 so that the following roller 6 can roll in the feeding direction Y at the predetermined position on the sheet S, and is capable of moving and rotating along with a behavior of the sheet S fed by the separate-feeding unit 3 together with the following roller 6, the three-axis accelerometer 8 capable of measuring accelerations in three directions acting on the roller supporting mechanism 207, and the error detecting unit 44 that detects a feed error of the sheet S based on the accelerations measured by the three-axis accelerometer 8.
Specifically, the error detecting unit 44 detects a feed error of the sheet S based on accelerations Gx, Gy, and Gz in the width direction X, the feeding direction Y, and the height direction Z, respectively, which act on the roller supporting mechanism 207 capable of moving and rotating along with a behavior of the sheet S together with the following roller 6. In this manner, with only one sensor, i.e., the three-axis accelerometer 8, behaviors of the following roller 6 and the roller supporting mechanism 207 can be sensed, and thereby sensing a behavior of the sheet S indirectly. Therefore, the sheet feeding device 201 can detect a plurality of types of feed errors separately with a compact and simple configuration.
FIGS. 9 and 10 are respectively a plan view and a side view of a sheet feeding device 301 according to a third embodiment of the present invention. The portions or components identical to those for the first embodiment are denoted with the same reference numerals, and the detailed description of those portions will not be repeated here. A difference between the sheet feeding devices 1 and 301 is that the sheet feeding device 301 includes an acceleration detecting unit 305 instead of the acceleration detecting unit 5.
A difference between the acceleration detecting units 5 and 305 is that the acceleration detecting unit 305 further includes an arm member 309.
A base end of the arm member 309 is fixed to the coupling plate 74 a, and the three-axis accelerometer 8 is arranged on a leading end of the arm member 309. The arm member 309 has a rod-like shape extending on the downstream side in the feeding direction Y when the following roller 6 and the roller supporting mechanism 7 are located in a proper position. The three-axis accelerometer 8 is arranged on the leading end of the arm member 309, i.e., the three-axis accelerometer 8 is arranged relatively far away from the rotating shaft of the following roller 6 and the roller supporting mechanism 7 that move along with the sheet S when there is a change in a behavior of the sheet S. Therefore, a radius of rotation of the three-axis accelerometer 8, which moves along with the following roller 6 and the roller supporting mechanism 7 when there is a change in a behavior of the sheet S, can be relatively long, and thereby increasing a moving amount of the three-axis accelerometer 8. As a result, even when there is a small change in a behavior of the sheet S, an acceleration acting on the three-axis accelerometer 8 can be amplified mechanically by the action of the arm member 309. Consequently, the three-axis accelerometer 8 can be sensitive to a slight movement of the sheet S as if there were a great change in a behavior of the sheet S, and a measurement value (an output value) of the three-axis accelerometer 8 can be amplified mechanically.
In this manner, the sheet feeding device 301 includes the following roller 6 capable of rolling by having line contact with a sheet S fed by the separate-feeding unit 3 on a line along the width direction X of the sheet S, the roller supporting mechanism 7 that supports the following roller 6 so that the following roller 6 can roll in the feeding direction Y at the predetermined position on the sheet S, and is capable of moving and rotating along with a behavior of the sheet S fed by the separate-feeding unit 3 together with the following roller 6, the three-axis accelerometer 8 capable of measuring accelerations in three directions acting on the roller supporting mechanism 7, and the error detecting unit 44 that detects a feed error of the sheet S based on the accelerations measured by the three-axis accelerometer 8.
Specifically, the error detecting unit 44 detects a feed error of the sheet S based on accelerations Gx, Gy, and Gz in the width direction X, the feeding direction Y, and the height direction Z, respectively, which act on the roller supporting mechanism 7 capable of moving and rotating along with a behavior of the sheet S together with the following roller 6. In this manner, with only one sensor, i.e., the three-axis accelerometer 8, behaviors of the following roller 6 and the roller supporting mechanism 7 can be sensed, and thereby sensing a behavior of the sheet S indirectly. Therefore, the sheet feeding device 301 can detect a plurality of types of feed errors separately with a compact and simple configuration.
Furthermore, the sheet feeding device 301 further includes the arm member 309. The base end of the arm member 309 is fixed to the roller supporting mechanism 7, and the three-axis accelerometer 8 is arranged on the leading end of the arm member 309. Therefore, even when there is a small change in a behavior of the sheet S, an acceleration acting on the three-axis accelerometer 8 can be amplified by the action of the arm member 309. Consequently, the three-axis accelerometer 8 can be sensitive to a slight movement of the sheet S as if there were a great change in a behavior of the sheet S, and a measurement value (an output value) of the three-axis accelerometer 8 can be amplified mechanically, so that it is possible to detect a feed error of the sheet S more reliably.
FIG. 11 is a block diagram of a sheet feeding device 401 according to a fourth embodiment of the present invention. The portions or components identical to those for the second embodiment are denoted with the same reference numerals, and the detailed description of those portions or components will not be repeated here. A difference between the sheet feeding devices 201 and 401 is that the sheet feeding device 401 includes an acceleration detecting unit 405 instead of the acceleration detecting unit 205. FIG. 12 is a perspective view of the acceleration detecting unit 405.
The acceleration detecting unit 405 includes a following roller 406, a roller supporting mechanism 407, the three-axis accelerometer 8, and a vibration applying unit 410. The following roller 406 rolls by having contact with a sheet S being fed. The roller supporting mechanism 407 supports the following roller 406.
As shown in FIG. 12, the roller supporting mechanism 407 rotatably supports the following roller 406 so that the following roller 406 can roll in the feeding direction Y at a predetermined position. The roller supporting mechanism 407 can move in the height direction Z and rotate around an axis along the height direction Z along with a behavior of the sheet S, at least. The roller supporting mechanism 407 includes a roller support shaft 471, a guide-shaft supporting member 473, and a roller-side support shaft 479.
The roller support shaft 471 is arranged along the width direction X, and serves as a rotating shaft of the following roller 406. The guide-shaft supporting member 473 includes a support plate 473 a and a guide shaft 473 b. The support plate 473 a is fixed to, for example, a casing (not shown) of the sheet feeding device 401. The guide shaft 473 b has a rod-like shape. A base end of the guide shaft 473 b is fixed to the support plate 473 a so that the guide shaft 473 b extends downward from the support plate 473 a in the height direction Z. One end of the roller-side support shaft 479 is integrally connected to one end of the roller support shaft 471. A guide hole 479 a extending in the height direction Z is formed on the other end of the roller-side support shaft 479. A leading end of the guide shaft 473 b is inserted into the guide hole 479 a. The roller-side support shaft 479 can move in the height direction Z with being guided by the guide shaft 473 b along with behaviors of the roller support shaft 471 and the following roller 406.
In other words, the roller supporting mechanism 407 can move up and down in the height direction Z along the guide shaft 473 b together with the following roller 406. When there is a change in a behavior of the sheet S due to uplift of the sheet S, and a force generated by the uplift of the sheet S acts on the following roller 406 and the roller supporting mechanism 407, the roller supporting mechanism 407 moves in the height direction Z along with the behavior of the sheet S together with the following roller 406. When there is a change in a behavior of the sheet S due to an occurrence of a cumulative skew of the sheet S, and a moment of rotation around the axis in the height direction Z acts on the following roller 406 and the roller supporting mechanism 407, the roller supporting mechanism 407 rotates around the guide shaft 473 b as the rotating shaft together with the following roller 406.
The vibration applying unit 410 applies a periodical vibration in the height direction Z to the three-axis accelerometer 8. The vibration applying unit 410 includes an eccentric cam groove 411, a slide shaft 412, and a slide guide 413. The eccentric cam groove 411 is formed on a side surface of the following roller 406 as a concave groove. The eccentric cam groove 411 is an annular groove which center is arranged with a shift of a predetermined distance from a central axis of the roller support shaft 471. In other words, the center of the eccentric cam groove 411 is eccentrically arranged with respect to the rotating shaft of the following roller 406. The slide shaft 412 has a rod-like shape, and a protruding portion 414 is formed on one end of the slide shaft 412. The slide guide 413 is fixed to, for example, the casing (not shown) of the sheet feeding device 401. The protruding portion 414 is inserted into the eccentric cam groove 411, and the other end of the slide shaft 412 is inserted into the slide guide 413, so that the slide shaft 412 is reciprocatably supported by the slide guide 413 so that the slide shaft 412 can reciprocate in the height direction Z. The three-axis accelerometer 8 is arranged on the other end of the slide shaft 412.
As the following roller 406 rolls by having contact with the sheet S being fed, the protruding portion 414 is guided along the eccentric cam groove 411, so that the slide shaft 412 reciprocates up and down in the height direction Z. In this manner, a periodical vibration in the height direction Z can be applied to the three-axis accelerometer 8 arranged on the end of the slide shaft 412. As a result, a measurement value of an acceleration Gz with a certain periodicity can be obtained from the three-axis accelerometer 8. In other words, the three-axis accelerometer 8 is periodically vibrated in the height direction Z in a positive way, so that it is possible to obtain a measurement value of the acceleration Gz with a stable period, phase, and amplitude depending on a feeding speed of the sheet S when the sheet S is fed properly. Therefore, it is possible to grasp a feeding status of the sheet S in more detail.
Specifically, as shown in FIG. 11, the processing unit 41 of the sheet feeding device 401 further includes a waveform generating unit 447 and a comparing unit 448. The waveform generating unit 447 generates an acceleration waveform of an acceleration in the height direction Z based on a measurement value of the acceleration Gz in the height direction Z. In this case, the acceleration waveform indicates an actually measured acceleration Gz with respect to a time T. The storing unit 42 of the sheet feeding device 401 stores therein a reference acceleration waveform depending on a feeding speed. The reference acceleration waveform is a reference waveform of an acceleration in the height direction Z depending on a feeding speed of the sheet S fed by the separate-feeding unit 3. For example, when a fluctuation in rolling of the following roller 406 occurs due to a jam or the like, the acceleration waveform generated by the waveform generating unit 447 does not match with the reference acceleration waveform. FIG. 13 is a graph of an example of an acceleration waveform of an acceleration in the height direction Z when no feed error occurs. FIG. 14 is a graph of an example of an acceleration waveform of an acceleration in the height direction Z when a feed error occurs. As shown in FIG. 13, when no feed error occurs, the acceleration waveform indicates a periodical waveform pattern matching with the reference acceleration waveform. On the other hand, as shown in FIG. 14, when a feed error occurs, the acceleration waveform indicates a nonperiodical waveform pattern or a scattering amplitude. Therefore, it is possible to grasp a feeding status of the sheet S in more detail based on a plurality of parameters for, for example, a period, an amplitude, and a phase of an acceleration waveform of the acceleration Gz. The comparing unit 448 compares an acceleration waveform generated by the waveform generating unit 447 with the reference acceleration waveform. The error detecting unit 44 of the sheet feeding device 401 detects a feed error of the sheet S based on a result of the comparison by the comparing unit 448.
A feed-error detecting process performed by the sheet feeding device 401 is explained in detail below with reference to a flowchart shown in FIG. 15. The control unit 4 determines whether a sheet S is being fed at this moment (Step S400). If the sheet S is not being fed at this moment (NO at Step S400), the counting unit 45 clears all values of each of counters for accelerations in each direction, and the feed-error detecting process is terminated as a normal end. If the sheet S is being fed at this moment (YES at Step S400), the control unit 4 selects a reference acceleration waveform depending on a feeding speed of the sheet S from those stored in the storing unit 42 (Step S402).
The control unit 4 acquires accelerations Gx, Gy, and Gz respectively in the width direction X, the feeding direction Y, and the height direction Z that are measured at predetermined sampling intervals by the three-axis accelerometer 8 (Step S404), and stores the acquired accelerations Gx, Gy, and Gz in a time trace buffer (not shown) of the storing unit 42 (Step S406). The waveform generating unit 447 generates an acceleration waveform of the acceleration in the height direction Z based on a measurement value of the acceleration Gz (Step S408).
The comparing unit 448 compares the acceleration waveform generated at Step S408 with the reference acceleration waveform selected at Step S402, and the control unit 4 determines whether an amplitude of the generated acceleration waveform matches with that of the reference acceleration waveform based on a result of the comparison by the comparing unit 448 (Step S410). For example, when a difference between the amplitudes of the generated acceleration waveform and the reference acceleration waveform exceeds an amplitude difference threshold, the control unit 4 determines that the generated acceleration waveform does not match with the reference acceleration waveform. If it is determined that the amplitude of the generated acceleration waveform does not match with that of the reference acceleration waveform (NO at Step S410), the error detecting unit 44 detects a feed error of the sheet S, and as error processes, the control unit 4 informs a user of an error, and the feeding stop unit 46 stops the feeding of the sheet S (Step S412). Then, the feed-error detecting process is terminated as an abnormal end.
If it is determined that the amplitude of the generated acceleration waveform matches with that of the reference acceleration waveform (YES at Step S410), the comparing unit 448 compares the acceleration waveform generated at Step S408 with the reference acceleration waveform selected at Step S402, and the control unit 4 determines whether a period of the generated acceleration waveform is delayed in comparison with that of the reference acceleration waveform based on a result of the comparison by the comparing unit 448 (Step S414). For example, when a delay in the period of the generated acceleration waveform in comparison with that of the reference acceleration waveform exceeds a period delay threshold, the control unit 4 determines that the period of the generated acceleration waveform is delayed in comparison with that of the reference acceleration waveform. If it is determined that the period of the generated acceleration waveform is delayed in comparison with that of the reference acceleration waveform (YES at Step S414), it can be assumed that the feeding speed of the sheet S is decreased, so that the error detecting unit 44 forecasts an occurrence of a jam before the jam occurs, and as error processes, the control unit 4 informs a user of an error, and the feeding stop unit 46 stops the feeding of the sheet S (Step S416). Then, the feed-error detecting process is terminated as the abnormal end.
If it is determined that the period of the generated acceleration waveform is not delayed in comparison with that of the reference acceleration waveform (NO at Step S414), the control unit 4 compares the currently-acquired accelerations Gx, Gy, and Gz with previously-acquired accelerations Gx, Gy, and Gz (Step S418), and the counting unit 45 determines whether the currently-acquired acceleration Gy increases (or decreases) as compared with the previously-acquired acceleration Gy (Step S420). If it is determined that the acceleration Gy increases (or decreases) (YES at Step S420), the counting unit 45 increments a value of a counter for the acceleration Gy by one. The error detecting unit 44 determines whether the increase (or decrease) of the acceleration Gy is continued for the predetermined time period based on whether the incremented value of the counter for the acceleration Gy reaches or exceeds a threshold (Step S422). If the error detecting unit 44 determines that the increase (or decrease) of the acceleration Gy is continued for the predetermined time period (YES at Step S422), and detects a skew of the sheet S, as error processes, the control unit 4 informs a user of an error, and the feeding stop unit 46 stops the feeding of the sheet S (Step S424). Then, the feed-error detecting process is terminated as the abnormal end.
If it is determined that the acceleration Gy does not increase (or decrease) (NO at Step S420), or if it is determined that the increase (or decrease) of the acceleration Gy is not continued for the predetermined time period (NO at Step S422), the counting unit 45 determines whether the currently-acquired acceleration Gx increases (or decreases) as compared with the previously-acquired acceleration Gx (Step S426). If it is determined that the acceleration Gx increases (or decreases) (YES at Step S426), the counting unit 45 increments a value of a counter for the acceleration Gx by one. The error detecting unit 44 determines whether the increase (or decrease) of the acceleration Gx is continued for the predetermined time period based on whether the incremented value of the counter for the acceleration Gx reaches or exceeds a threshold (Step S428). If the error detecting unit 44 determines that the increase (or decrease) of the acceleration Gx is continued for the predetermined time period (YES at Step S428), and detects a skew of the sheet S, as error processes, the control unit 4 informs a user of an error, and the feeding stop unit 46 stops the feeding of the sheet S (Step S430). Then, the feed-error detecting process is terminated as the abnormal end. If it is determined that the acceleration Gx does not increase (or decrease) (NO at Step S426), or it is determined that the increase (or decrease) of the acceleration Gx is not continued for the predetermined time period (NO at Step S428), the process control returns to Step S400.
In this manner, the sheet feeding device 401 includes the following roller 406 capable of rolling by having line contact with a sheet S fed by the separate-feeding unit 3 on a line along the width direction X of the sheet S, the roller supporting mechanism 407 that supports the following roller 406 so that the following roller 406 can roll in the feeding direction Y at the predetermined position on the sheet S, and is capable of moving and rotating along with a behavior of the sheet S fed by the separate-feeding unit 3 together with the following roller 406, the three-axis accelerometer 8 capable of measuring accelerations in three directions acting on the roller supporting mechanism 407, and the error detecting unit 44 that detects a feed error of the sheet S based on the accelerations measured by the three-axis accelerometer 8.
Specifically, the error detecting unit 44 detects a feed error of the sheet S based on accelerations Gx, Gy, and Gz in the width direction X, the feeding direction Y, and the height direction Z, respectively, which act on the roller supporting mechanism 407 capable of moving and rotating along with a behavior of the sheet S together with the following roller 406. In this manner, with only one sensor, i.e., the three-axis accelerometer 8, behaviors of the following roller 406 and the roller supporting mechanism 407 can be sensed, and thereby sensing a behavior of the sheet S indirectly. Therefore, the sheet feeding device 401 can detect a plurality of types of feed errors separately with a compact and simple configuration.
Furthermore, the sheet feeding device 401 includes the vibration applying unit 410 that applies a periodical vibration in the height direction Z to the three-axis accelerometer 8, the waveform generating unit 447 that generates an acceleration waveform of an acceleration in the height direction Z based on a measurement value of the acceleration Gz in the height direction Z, the storing unit 42 that stores therein a reference acceleration waveform as a reference of an acceleration waveform in the height direction Z depending on a feeding speed of the sheet S fed by the separate-feeding unit 3, and the comparing unit 448 that compares the acceleration waveform generated by the waveform generating unit 447 with the reference acceleration waveform. The error detecting unit 44 detects a feed error of the sheet S based on a result of the comparison by the comparing unit 448. Therefore, the three-axis accelerometer 8 is periodically vibrated in the height direction Z in a positive way, so that it is possible to obtain a measurement value of the acceleration Gz with a stable period, phase, and amplitude. Consequently, it is possible to grasp a feeding status of the sheet S in more detail based on a plurality of parameters for, for example, a period, an amplitude, and a phase of an acceleration waveform of the acceleration Gz.
Incidentally, the vibration applying unit 410 including the eccentric cam groove 411, the slide shaft 412, and the slide guide 413 is employed in the fourth embodiment. As long as it is possible to apply a periodical vibration in the height direction Z to the three-axis accelerometer 8, a vibration applying unit with a different configuration can be employed.
According to the embodiments of the present invention, a sheet feeding device detects a feed error of a sheet based on accelerations in three directions (or dimensions) acting on a supporting member capable of moving and rotating along with a behavior of the sheet together with a rolling member. Therefore, with a compact and simple configuration, it is possible to detect a plurality of types of feed errors occurring while the sheet is being fed before a damage to the sheet due to the feed error occurs.
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.

Claims

1. A sheet feeding device comprising:

a feeding unit that feeds a sheet;

a rolling member that rolls by having contact with the sheet being fed by the feeding unit;

a supporting member that moves along with a behavior of the sheet with supporting the rolling member so that the rolling member rolls in a feeding direction of the sheet at a predetermined position on the sheet;

an acceleration measuring unit that measures accelerations acting on the supporting member in three directions; and

a detecting unit that detects a feed error of the sheet based on the accelerations measured by the acceleration measuring unit.

2. The sheet feeding device according to claim 1, wherein

the acceleration measuring unit measures accelerations in the feeding direction, a width direction horizontally-perpendicular to the feeding direction, and a height direction perpendicular to both the feeding direction and the width direction, and

the supporting member moves in the height direction and rotates around an axis along the height direction along with the behavior of the sheet.

3. The sheet feeding device according to claim 2, wherein the detecting unit detects a skew of the sheet as a feed error of the sheet when an increase or decrease of any of the accelerations in the feeding direction and the width direction is continued for a predetermined time period.

4. The sheet feeding device according to claim 2, wherein the detecting unit detects a jam of the sheet as a feed error of the sheet when an increase or decrease of the acceleration in the height direction is continued for a predetermined time period.

5. The sheet feeding device according to claim 2, further comprising

a vibration applying unit that applies a periodical vibration in the height direction to the acceleration measuring unit;

a waveform generating unit that generates an acceleration waveform of the acceleration in the height direction based on a result of measurement by the acceleration measuring unit;

a storing unit that stores therein a reference acceleration waveform as a reference of the acceleration waveform in the height direction depending on a feeding speed of the sheet fed by the feeding unit; and

a comparing unit that compares the acceleration waveform generated by the waveform generating unit with the reference acceleration waveform, wherein

the detecting unit detects a feed error of the sheet based on a result of comparison by the comparing unit.

6. The sheet feeding device according to claim 1, wherein the rolling member has a cylindrical shape, and a rotating shaft of the rolling member is arranged along the width direction.

7. The sheet feeding device according to claim 1, further comprising an arm member having a base end portion and a leading end portion, wherein

the base end portion of the arm member is fixed to the supporting member and the acceleration measuring unit is provided on the leading end portion of the arm member.

8. The sheet feeding device according to claim 1, further comprising a stacking member on which a plurality of sheets are stacked, wherein

the feeding unit includes a separating unit that separates the sheets stacked on the stacking member one by one, and

the rolling member is arranged on an upstream side of the separating unit in the feeding direction.

9. The sheet feeding device according to claim 1, further comprising a feeding stop unit that stops a feeding of the sheet by the feeding unit depending on a result of detection by the detecting unit.

10. The sheet feeding device according to claim 1, wherein the rolling member has point contact with the sheet at a plurality of points located along a width direction horizontally-perpendicular to the feeding direction.

11. The sheet feeding device according to claim 1, wherein the rolling member has line contact with the sheet on a line along a width direction horizontally-perpendicular to the feeding direction.