U.S. patent application number 12/106633 was filed with the patent office on 2009-01-08 for sheet feeding device.
This patent application is currently assigned to PFU LIMITED. Invention is credited to Yuki KASAHARA, Koichi MINAMI, Masaya TAKAMORI, Nobuhisa YAMAZAKI.
Application Number | 20090008861 12/106633 |
Document ID | / |
Family ID | 40121642 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090008861 |
Kind Code |
A1 |
KASAHARA; Yuki ; et
al. |
January 8, 2009 |
SHEET FEEDING DEVICE
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.
Inventors: |
KASAHARA; Yuki; (ISHIKAWA,
JP) ; MINAMI; Koichi; (ISHIKAWA, JP) ;
YAMAZAKI; Nobuhisa; (ISHIKAWA, JP) ; TAKAMORI;
Masaya; (ISHIKAWA, JP) |
Correspondence
Address: |
LOWE HAUPTMAN HAM & BERNER, LLP
1700 DIAGONAL ROAD, SUITE 300
ALEXANDRIA
VA
22314
US
|
Assignee: |
PFU LIMITED
ISHIKAWA
JP
|
Family ID: |
40121642 |
Appl. No.: |
12/106633 |
Filed: |
April 21, 2008 |
Current U.S.
Class: |
271/10.03 |
Current CPC
Class: |
B65H 2513/20 20130101;
B65H 2801/06 20130101; B65H 2511/52 20130101; B65H 2511/528
20130101; B65H 2553/62 20130101; B65H 2511/52 20130101; B65H
2557/24 20130101; B65H 2557/23 20130101; B65H 2220/01 20130101;
B65H 2513/20 20130101; B65H 2220/03 20130101; B65H 2220/03
20130101; B65H 7/06 20130101; B65H 2511/528 20130101 |
Class at
Publication: |
271/10.03 |
International
Class: |
B65H 7/00 20060101
B65H007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2007 |
JP |
2007-178953 |
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.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] 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.
[0003] 2. Description of the Related Art
[0004] 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.
[0005] 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.
[0006] 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
[0007] It is an object of the present invention to at least
partially solve the problems in the conventional technology.
[0008] 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.
[0009] 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
[0010] FIG. 1 is a block diagram of a sheet feeding device
according to a first embodiment of the present invention;
[0011] FIG. 2 is a plan view of the sheet feeding device according
to the first embodiment;
[0012] FIG. 3 is a side view of the sheet feeding device according
to the first embodiment;
[0013] FIG. 4A is a plan view of an acceleration detecting unit
according to the first embodiment;
[0014] FIG. 4B is a front view of the acceleration detecting unit
according to the first embodiment;
[0015] FIG. 4C is a side view of the acceleration detecting unit
according to the first embodiment;
[0016] 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;
[0017] 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;
[0018] FIG. 7 is a flowchart of a feed-error detecting process
performed by the sheet feeding device according to the first
embodiment;
[0019] 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;
[0020] FIG. 8B is a front view of the acceleration detecting unit
according to the second embodiment;
[0021] FIG. 8C is a side view of the acceleration detecting unit
according to the second embodiment;
[0022] FIG. 9 is a plan view of a sheet feeding device according to
a third embodiment of the present invention;
[0023] FIG. 10 is a side view of the sheet feeding device according
to the third embodiment;
[0024] FIG. 11 is a block diagram of a sheet feeding device
according to a fourth embodiment of the present invention;
[0025] FIG. 12 is a perspective view of an acceleration detecting
unit of the sheet feeding device according to the fourth
embodiment;
[0026] 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;
[0027] 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
[0028] 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
[0029] Exemplary embodiments of the present invention are explained
in detail below with reference to the accompanying drawings.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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".
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] The separation roller 31 is connected to a drive motor 31a
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 31a. 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.
[0041] 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.
[0042] The control unit 4 includes a microcomputer, and controls
the sheet feeding device 1. The control unit 4 is connected to the
drive motor 31a, 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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 74a and 74b. The coupling plates 74a and 74b are arranged in
such a way that a side surface of each of the coupling plates 74a
and 74b 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 74a is located on the downstream
side, and the coupling plate 74b is located on the upstream side in
the feeding direction Y.
[0051] 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 74a and 74b 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.
[0052] 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.
[0053] 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.
[0054] The three-axis accelerometer 8 is provided on the coupling
plate 74a, 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.
[0055] 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 31a and the three-axis accelerometer 8
are connected to the processing unit 41 via the input/output unit
43.
[0056] 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.
[0057] 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).
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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 31a 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.
[0068] 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).
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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.
[0087] 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.
[0088] The roller supporting member 273 includes a support plate
273a and a guide shaft 273b. The support plate 273a is fixed to,
for example, a casing (not shown) of the sheet feeding device 201.
The guide shaft 273b has a rod-like shape. A base end of the guide
shaft 273b is fixed to the support plate 273a so that the guide
shaft 273b extends downward from the support plate 273a in the
height direction Z. The supporting-member-side coupling member 275
has a guide hole 275a extending in the height direction Z. A
leading end of the guide shaft 273b is inserted into the guide hole
275a. The supporting-member-side coupling member 275 can move in
the height direction Z with being guided by the guide shaft 273b.
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.
[0089] Therefore, the roller supporting mechanism 207 can move up
and down in the height direction Z along the guide shaft 273b
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 273b as a
rotating shaft together with the following roller 6.
[0090] 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.
[0091] 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.
[0092] 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.
[0093] A difference between the acceleration detecting units 5 and
305 is that the acceleration detecting unit 305 further includes an
arm member 309.
[0094] A base end of the arm member 309 is fixed to the coupling
plate 74a, 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.
[0095] 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.
[0096] 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.
[0097] 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.
[0098] 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.
[0099] 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.
[0100] 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.
[0101] 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
473a and a guide shaft 473b. The support plate 473a is fixed to,
for example, a casing (not shown) of the sheet feeding device 401.
The guide shaft 473b has a rod-like shape. A base end of the guide
shaft 473b is fixed to the support plate 473a so that the guide
shaft 473b extends downward from the support plate 473a 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 479a 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 473b is inserted into the guide hole 479a. The
roller-side support shaft 479 can move in the height direction Z
with being guided by the guide shaft 473b along with behaviors of
the roller support shaft 471 and the following roller 406.
[0102] In other words, the roller supporting mechanism 407 can move
up and down in the height direction Z along the guide shaft 473b
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 473b
as the rotating shaft together with the following roller 406.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] 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).
[0107] 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).
[0108] 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.
[0109] 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.
[0110] 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.
[0111] 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.
[0112] 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.
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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.
* * * * *