U.S. patent application number 15/052284 was filed with the patent office on 2017-01-19 for sheet transport device, image reading device, and image forming apparatus.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Takato KATO, Kazuyuki KODA, Masato SERIKAWA, Takakiyo TOBA.
Application Number | 20170015520 15/052284 |
Document ID | / |
Family ID | 57749161 |
Filed Date | 2017-01-19 |
United States Patent
Application |
20170015520 |
Kind Code |
A1 |
SERIKAWA; Masato ; et
al. |
January 19, 2017 |
SHEET TRANSPORT DEVICE, IMAGE READING DEVICE, AND IMAGE FORMING
APPARATUS
Abstract
A sheet transport device includes a transport unit that
transports a sheet to a reading position by a first transport
roller, a driving unit that switches a rotating direction, a
rotating unit that rotates the first transport roller in one
direction, the rotating unit including a one-direction gear that
directly meshes with a first planet gear when the driving unit
rotates in a first direction and meshes with a second planet gear
when the driving unit rotates in a second direction, a switch unit
that switches between states in which rotation of the one-direction
gear is or is not transmitted to the first transport roller, and a
displacement-force applying part that applies a force for
displacing the first planet gear to mesh with the one-direction
gear when the first planet gear touches the switch unit.
Inventors: |
SERIKAWA; Masato; (Kanagawa,
JP) ; TOBA; Takakiyo; (Kanagawa, JP) ; KODA;
Kazuyuki; (Kanagawa, JP) ; KATO; Takato;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
57749161 |
Appl. No.: |
15/052284 |
Filed: |
February 24, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 5/062 20130101;
B65H 2403/724 20130101; B65H 2301/1321 20130101; B65H 2404/1442
20130101; B65H 29/125 20130101; B65H 85/00 20130101; B65H 2403/481
20130101; B65H 2301/33312 20130101; B65H 29/14 20130101; F16H
55/0873 20130101; F16H 2055/0866 20130101; B65H 9/006 20130101;
B65H 2801/39 20130101 |
International
Class: |
B65H 85/00 20060101
B65H085/00; B65H 5/36 20060101 B65H005/36; B65H 5/06 20060101
B65H005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2015 |
JP |
2015-143346 |
Claims
1. A sheet transport device comprising: a transport unit that
transports a sheet to a reading position by a first transport
roller and transports the sheet to the first transport roller by
switching back and inverting the sheet by a second transport roller
after the sheet passes through the reading position; a single
driving unit that switches a rotating direction thereof between
first and second directions; a rotating unit that rotates the first
transport roller in one direction regardless of the rotating
direction of the driving unit, the rotating unit including a sun
gear driven by the driving unit, first and second planet gears
meshed with the sun gear, and a one-direction gear that directly
meshes with the first planet gear when the driving unit rotates in
the first direction and meshes with the second planet gear with an
intermediate gear being disposed therebetween when the driving unit
rotates in the second direction; a switch unit that switches
between states in which rotation of the one-direction gear is
transmitted and not transmitted to the first transport roller, the
switch unit being disposed in one axial end portion of the
one-direction gear and having a cylindrical exterior; and a
displacement-force applying part provided in the first planet gear
or the switch unit to apply a force for displacing the first planet
gear in a direction to mesh with the one-direction gear when an
outer peripheral end of the first planet gear touches the switch
unit.
2. The sheet transport device according to claim 1, wherein the
displacement-force applying part is formed by an inclined surface
provided in an axial end portion of an outer periphery of the first
planet gear or the switch unit.
3. The sheet transport device according to claim 1, wherein a
leading edge of the sheet transported from an upstream side of the
first transport roller abuts on the first transport roller to
correct skew of the sheet when the rotation of the one-direction
gear is not transmitted by the switch unit and the first transport
roller is stopped.
4. The sheet transport device according to claim 2, wherein a
leading edge of the sheet transported from an upstream side of the
first transport roller abuts on the first transport roller to
correct skew of the sheet when the rotation of the one-direction
gear is not transmitted by the switch unit and the first transport
roller is stopped.
5. The sheet transport device according to claim 1, wherein the
second transport roller has a release unit that releases a
transport force for the sheet when the rotating direction is
switched by the driving unit after the second transport roller
switches back and transports the sheet to the first transport
roller.
6. The sheet transport device according to claim 2, wherein the
second transport roller has a release unit that releases a
transport force for the sheet when the rotating direction is
switched by the driving unit after the second transport roller
switches back and transports the sheet to the first transport
roller.
7. The sheet transport device according to claim 3, wherein the
second transport roller has a release unit that releases a
transport force for the sheet when the rotating direction is
switched by the driving unit after the second transport roller
switches back and transports the sheet to the first transport
roller.
8. The sheet transport device according to claim 4, wherein the
second transport roller has a release unit that releases a
transport force for the sheet when the rotating direction is
switched by the driving unit after the second transport roller
switches back and transports the sheet to the first transport
roller.
9. An image reading device comprising: the sheet transport device
according to claim 1; and an image reading unit that reads an image
from a sheet transported by the sheet transport device.
10. An image forming apparatus comprising: the image reading device
according to claim 9; and an image forming part that forms an image
read by the image reading device on a recording medium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2015-143346 filed Jul.
17, 2015.
BACKGROUND
Technical Field
[0002] The present invention relates to a sheet transport device,
an image reading device, and an image forming apparatus.
SUMMARY
[0003] According to an aspect of the invention, there is provided a
sheet transport device including a transport unit that transports a
sheet to a reading position by a first transport roller and
transports the sheet to the first transport roller by switching
back and inverting the sheet by a second transport roller after the
sheet passes through the reading position, a single driving unit
that switches a rotating direction thereof between first and second
directions, a rotating unit that rotates the first transport roller
in one direction regardless of the rotating direction of the
driving unit, the rotating unit including a sun gear driven by the
driving unit, first and second planet gears meshed with the sun
gear, and a one-direction gear that directly meshes with the first
planet gear when the driving unit rotates in the first direction
and meshes with the second planet gear with an intermediate gear
being disposed therebetween when the driving unit rotates in the
second direction, a switch unit that switches between states in
which rotation of the one-direction gear is transmitted and not
transmitted to the first transport roller, the switch unit being
disposed in one axial end portion of the one-direction gear and
having a cylindrical exterior, and a displacement-force applying
part provided in the first planet gear or the switch unit to apply
a force for displacing the first planet gear in a direction to mesh
with the one-direction gear when an outer peripheral end of the
first planet gear touches the switch unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Exemplary embodiments of the present invention will be
described in detail based on the following figures, wherein:
[0005] FIG. 1 is an overall configuration view of an image forming
apparatus to which an image reading device according to a first
exemplary embodiment of the present invention is applied;
[0006] FIG. 2 is a structural view of the image reading device
according to the first exemplary embodiment;
[0007] FIG. 3 is a structural view of a sheet transport device
according to the first exemplary embodiment;
[0008] FIG. 4 is a structural perspective view of the sheet
transport device of the first exemplary embodiment;
[0009] FIG. 5 is a structural front view of the sheet transport
device of the first exemplary embodiment;
[0010] FIG. 6 is a structural plan view of the sheet transport
device of the first exemplary embodiment;
[0011] FIG. 7 is a structural perspective view illustrating the
principal part of the sheet transport device of the first exemplary
embodiment;
[0012] FIG. 8 is a cross-sectional structural view of an
electromagnetic clutch;
[0013] FIG. 9 is a structural perspective view of an output
roller;
[0014] FIG. 10 is a structural perspective view of a tooth-lacking
gear;
[0015] FIG. 11A is a structural view illustrating a state in which
one engaging portion of the tooth-lacking gear is engaged with a
distal end portion of a solenoid, and FIG. 11B is a structural view
illustrating a state in which the engaging portion of the
tooth-lacking gear is disengaged from the distal end portion of the
solenoid;
[0016] FIG. 12A is a structural view illustrating an intermediate
state in which a cam portion of the tooth-lacking gear turns, and
FIG. 12B is a structural view illustrating a state in which the cam
portion of the tooth-lacking gear is stopped;
[0017] FIG. 13A is a structural perspective view illustrating a
state in which an end portion of a first planet gear is in contact
with a first electromagnetic clutch, and FIG. 13B is a structural
perspective view illustrating a state in which the first planet
gear is displaced in a direction to mesh with a one-direction
gear;
[0018] FIG. 14 is a structural perspective view illustrating the
principal part of a sheet transport device of the related art;
[0019] FIG. 15 is an explanatory view showing the function of the
sheet transport device of the first exemplary embodiment;
[0020] FIGS. 16-1 to 16-8 are explanatory views illustrating the
action of the sheet transport device of the first exemplary
embodiment; and
[0021] FIG. 17 is a structural perspective view illustrating the
principal part of a sheet transport device according to a second
exemplary embodiment of the present invention.
DETAILED DESCRIPTION
[0022] Exemplary embodiments of the present invention will be
described below with reference to the drawings.
First Exemplary Embodiment
[0023] FIG. 1 is an overall configuration view illustrating the
outline of an image forming apparatus to which a sheet transport
device and an image reading device according to a first exemplary
embodiment of the present invention are applied.
Overall Configuration of Image Forming Apparatus
[0024] An image forming apparatus 1 according to the first
exemplary embodiment is configurated as a color copying machine as
an example. The image forming apparatus 1 includes an image reading
device 3 that reads an image on a document 6 serving as an example
of a sheet, and an image forming section 2 serving as an example of
an image forming part that forms an image on a recording medium,
for example, on the basis of image data read by the image reading
device 3 and image data transmitted from an external personal
computer. The image reading device 3 is disposed above an apparatus
body 1a that houses the image forming section 2 while being
supported by a support section 4. Between the image reading device
3 and the apparatus body 1a, a space is provided so that a
recording medium on which an image is formed is output
therethrough.
[0025] As illustrated in FIG. 1, the image reading device 3 is
provided with a control panel 66 serving as an operating unit used
to operate the image forming apparatus 1 and the image reading
device 3. The control panel 66 is provided in an upper part of a
front wall 311 located on the front of a housing 31 of the image
reading device 3. The control panel 66 includes a touch panel 67
and plural operation buttons 68. The touch panel 67 also functions
as a display unit for displaying an operation menu, a warning, a
message, and so on to the user, and receives various settings for
the displayed operation menu.
[0026] The image forming section 2 includes plural image forming
devices 10 each of which forms a toner image developed with toner
contained in developer, an intermediate transfer device 20 that
holds toner images formed by the image forming devices 10 and
transports the toner images to a second transfer position where the
toner images are to be finally second-transferred onto recording
paper 5 serving as an example of a recording medium, a paper
feeding device 50 that stores and transports required recording
paper 5 to be supplied to the second transfer position in the
intermediate transfer device 20, and a fixing device 40 that fixes
the toner images second-transferred on the recording paper 5 in the
intermediate transfer device 20. The apparatus body 1a is composed
of a support structural member, an exterior covering, and so on.
The image forming section 2 is not limited to the
electrophotographic system, but may adopt another system, such as
an inkjet system, a thermal head system, or a lithographic system,
as long as it can form images on recording media.
[0027] The paper feeding device 50 is disposed to be located below
an exposure device 13. The paper feeding device 50 principally
includes plural (or singular) sheet containers 51 (51.sub.1 to
51.sub.4) that contain recording paper 5 of a desired size, type,
and so on, and feeding devices 52 and 53 that feed out the
recording paper 5 one by one from the sheet containers 51.sub.1 to
51.sub.4. For example, the sheet containers 51 are mounted to be
drawn out toward the front side of the apparatus body 1a (a side
surface the user faces during operation).
[0028] Between the paper feeding device 50 and the intermediate
transfer device 20, a paper feeding and transporting path 56 is
provided to transport recording paper 5 fed from the paper feeding
device 50 to the second transfer position. The paper feeding and
transporting path 56 includes plural paper transport rollers 54 and
55 and unillustrated transport guides. The paper transport roller
55 disposed at a position just before the second transfer position
in the paper feeding and transporting path 56 is configurated, for
example, as a roller for adjusting the transport time of the
recording paper 5 (registration roller). On the downstream side of
the fixing device 40 in the sheet transport direction, a transport
roller 58 and an output roller 59 are disposed to output the
recording paper 5 to an output container 57 provided in the upper
part of the apparatus body 1a.
[0029] The plural image forming devices 10 are formed by four image
forming devices 10Y, 10M, 10C, and 10K that form toner images of
four colors of yellow (Y), magenta (M), cyan (C), and black (K),
respectively. Each of the image forming devices 10 (Y, M, C, and K)
includes a rotary photoconductor drum 11 serving as an example of
an image carrier, a charging device 12 that charges a peripheral
surface (image bearing surface) of the photoconductor drum 11, on
which an image can be formed, with a required potential, an
exposure device 13 that forms an electrostatic latent image (for
the corresponding color) having a potential difference by radiating
light LB based on image information (signals) onto the charged
peripheral surface of the photoconductor drum 11, a developing
device 14 that develops the electrostatic latent image with toner
of developer of the corresponding color (Y, M, C, or K) into a
toner image, a first transfer device 15 that transfers the toner
image onto the intermediate transfer device 20, and a drum cleaning
device 16 that cleans the photoconductor drum 11 by removing
attached substances, such as toner, remaining on the image bearing
surface of the photoconductor drum 11 after first transfer.
[0030] The intermediate transfer device 20 includes an intermediate
transfer belt 21, plural transport rollers 22 to 26 that transport
the intermediate transfer belt 21 in a direction of arrow, and a
belt cleaning device 27 that cleans a surface of the intermediate
transfer belt 21 by removing attached substances, such as toner,
remaining on and attached to the surface of the intermediate
transfer belt 21. A second transfer roller 28 serving as a second
transfer device for second-transferring toner images on the
intermediate transfer belt 21 together onto recording paper 5 is
disposed in contact with the transport roller 26 with the
intermediate transfer belt 21 being disposed therebetween.
[0031] The fixing device 40 includes a heating rotating body 41 and
a pressurizing rotating body 42. A contact portion between the
heating rotating body 41 and the pressurizing rotating body 42
forms a fixing portion that fixes the toner images on the recording
paper 5.
[0032] The image forming apparatus 1 further includes a duplex unit
60 that forms images on both surfaces of recording paper 5. When
recording paper 5 having an image formed on one surface is
transported to the output container 57 by the output roller 59, it
is introduced into the duplex unit 60 through a switch gate 61 by
rotating the output roller 59 in an opposite direction while the
output roller 59 holds a trailing edge of the recording paper 5.
The duplex unit 60 includes a duplex transport path 65 composed of
plural transport rollers 62 to 64 for transporting the introduced
recording paper 5 in an inverted state, and unillustrated transport
guides.
[0033] In FIG. 1, each toner cartridge 140 (Y, M, C, or K) serves
as a developer container that stores developer including at least
toner to be supplied to the corresponding developing device 14. In
the first exemplary embodiment, only toner is stored inside the
toner cartridge 140.
[0034] A control device 100 controls an image forming operation of
the image forming apparatus 1 and an image reading operation of the
image reading device 3. A control device for controlling the image
reading operation of the image reading device 3 may be provided
separately from a control device for the image forming apparatus
1.
Basic Operation of Image Forming Apparatus
[0035] The basic image forming operation of the image forming
apparatus 1 will be described below.
[0036] Here, a description will be given of an image forming
operation of forming a full-color image by combining toner images
of four colors (Y, M, C, and K) using the four image forming
devices 10 (Y, M, C, and K).
[0037] When the image forming apparatus 1 receives command
information about a request for an image forming operation
(printing), the four image forming devices 10 (Y, M, C, and K), the
intermediate transfer device 20, the second transfer roller 28, the
fixing device 40, and so on start.
[0038] In the image forming devices 10 (Y, M, C, and K), toner
images of four colors (Y, M, C, and K) are visualized by being
developed with the corresponding color toners, for example, on the
basis of image data on the surface (first surface) of the document
6 read by the image reading device 3. When the color toner images
formed in the image forming devices 10 (Y, M, C, and K) are
transported to the first transfer positions, the first transfer
devices 15 first-transfer and superimpose the color toner images in
order on the intermediate transfer belt 21 that rotates in the
direction of the arrow in the intermediate transfer device 20.
Next, in the intermediate transfer device 20, the first-transferred
toner images are held and transported to the second transfer
position by the rotation of the intermediate transfer belt 21. On
the other hand, in the paper feeding device 50, required recording
paper 5 is fed out to the paper feeding and transporting path 56 in
response to the image forming operation. In the paper feeding and
transporting path 56, the paper transport roller 55 serving as the
registration roller feeds and supplies the recording paper 5 to the
second transfer position in accordance with the transfer time.
[0039] At the second transfer position, the second transfer roller
28 second-transfers the toner images on the intermediate transfer
belt 21 together onto the recording paper 5. In the intermediate
transfer device 20 after the second transfer is finished, the belt
cleaning device 27 cleans the surface of the intermediate transfer
belt 21 by removing attached substances, such as toner, remaining
on the surface of the intermediate transfer belt 21 after the
second transfer.
[0040] Next, the recording paper 5 on which the toner images are
second-transferred is separated from the intermediate transfer belt
21 and the second transfer roller 28, and is then transported to
the fixing device 40. In the fixing device 40, the unfixed toner
images are fixed on the recording paper 5 by a necessary fixing
operation (heating and pressurization). Finally, after fixing is
completed, the recording paper 5 is output to, for example, the
output container 57 disposed in the upper part of the apparatus
body 1a by the transport roller 58 and the output roller 59.
[0041] In a case in which images are formed on both surfaces of
recording paper 5, when the recording paper 5 is transported to the
output container 57 by the output roller 59 after an image is
formed on one surface of the recording paper 5, the rotating
direction of the output roller 59 is switched to the opposite
direction while the output roller 59 holds a trailing edge of the
recording paper 5. The transport direction of the recording paper 5
transported in the opposite direction by the output roller 59 is
switched toward the duplex unit 60 by the switch gate 61. After
that, the recording paper 5 is transported to the paper transport
roller 55 in an inverted state through the duplex transport path 65
including the transport rollers 62 to 64. The paper transport
roller 55 sends and supplies the recording paper 5 to the second
transfer position in accordance with the transfer time. Then, a
toner image is second-transferred from the intermediate transfer
belt 21 onto a back surface (second surface) of the recording paper
5, for example, on the basis of image data on the back surface
(second surface) of the document 6 read by the image reading device
3. The recording paper 5 on which the toner image is
second-transferred is subjected to fixing in the fixing device 40.
The recording paper 5 is then output with the second surface facing
down to the output container 57 disposed in the upper part of the
apparatus body 1a by the output roller 59.
[0042] Through the above procedure, the recording paper 5 on which
a full-color image is formed by combining toner images of four
colors is output. In the image forming apparatus 1, a monochromatic
image is formed on recording paper 5 by using only the image
forming device 10K for black (K). Structure of Image Reading
Device
[0043] FIG. 2 schematically illustrates the structure of the image
reading device 3 to which the sheet transport device of the first
exemplary embodiment is applied.
[0044] The image reading device 3 roughly includes a housing 31
having a document reading surface on its upper surface, a document
press covering 32 openably and closably attached to the housing 31,
and a duplex automatic document feeder (DADF) 33 provided at one
end (left end in FIG. 2) of the document press covering 32.
[0045] The image reading device 3 is configurated to switch, in
response to the operation of the user, the mode of the image
reading device 3 between a first reading mode for reading images on
front surfaces and back surfaces of documents 6 while automatically
transporting the documents 6 one by one by the DADF 33 and a second
reading mode for reading an image on a document 6 placed on a
document table 83 to be described later. FIG. 2 illustrates states
of the members when document reading is performed in the first
reading mode.
[0046] The DADF 33 includes a document transport mechanism that is
composed of a document storage unit 70, a nudger roller 71, a feed
roller 72, a pressure pad 72a, a first transport roller 73,
transport rollers 74 and 75, and an output roller 77. The document
storage unit 70 can store plural stacked documents 6 while read
surfaces (first surfaces) of the documents 6 face up. The nudger
roller 71 feeds out the documents 6 from the document storage unit
70. The feed roller 72 loosens and supplies the documents 6 fed out
by the nudger roller 71 one by one. The pressure pad 72a loosens
the documents 6 one by one while being in pressure contact with the
feed roller 72. The first transport roller 73 transports a fed
document 6 to the reading position. The transport rollers 74 and 75
transport the document 6 transported by the first transport roller
73 so that the document 6 passes through the reading position. The
output roller 77 serves as an example of a second transport roller
that outputs the document 6 to an output storage unit 76. The
nudger roller 71, the feed roller 72, the transport rollers 73 to
75, and the output roller 77 are driven by a driving unit (to be
described later) during reading of the document 6. The first
transport roller 73 is a registration roller that adjusts the
transport time of the document 6 to the reading position. Although
not explicitly stated in the first exemplary embodiment, the terms
"transport roller" and "output roller" include a pair of
rollers.
[0047] The first transport roller 73 also functions as a correction
unit that mechanically corrects the tilt of the document 6 with
respect to the transport direction (hereinafter, referred to as
"skew correction") so that the direction of edges of the document 6
becomes the same as the transport direction. As illustrated in FIG.
2, a transport roller 73b serving as a driving roller in the first
transport roller 73 is driven by, for example, a driving unit to be
described later, such as a driving motor, so as to rotate in a
forward direction Ra in FIG. 2 from a stopped state at a
predetermined timing. A transport roller 73a serving as a driven
roller rotates to follow the transport roller 73b while being in
pressure contact with the transport roller 73b.
[0048] In the first transport roller 73, while the transport roller
73b serving as the driving roller is stopped, a leading edge of the
document 6 transported by the feed roller 72 located on the
upstream side in the transport direction of the document 6 abuts on
a pressure contact portion between the transport roller 73b and the
transport roller 73a. The first transport roller 73 performs skew
correction by starting to transport the document 6 after bending a
leading end region of the document 6 so that the leading edge of
the document 6 coincides with the axial direction of the first
transport roller 73.
[0049] The DADF 33 further includes a curved reading guide 78, a
back-surface support member 80, a first size detection sensor 81,
and a second size detection sensor 82. The reading guide 78 guides
the document 6 to the reading position and further guides the
document 6 from the reading position in the output direction. The
back-surface support member 80 is provided on the reading guide 78
above a reading window 79 to support a back surface of the document
6. The first size detection sensor 81 is provided in the document
storage unit 70 to detect the size of the document 6 in the
sub-scanning direction. The second size detection sensor 82 is
similarly provided in the document storage unit 70 to detect the
size of the document 6 in the sub-scanning direction.
[0050] The housing 31 of the image reading device 3 is provided as
a box shaped like a rectangular parallelepiped whose upper end
surface is partly open. The housing 31 includes an upper wall 312
opposed to the document press covering 32, a bottom wall 313
opposed to the upper wall 312, a side wall 314 and a side wall 315
opposed to each other in the sub-scanning direction (a right-left
direction in FIG. 2) with the bottom wall 313 being disposed
therebetween, the above-described front wall 311 (see FIG. 1), and
a rear wall 316 opposed to the front wall 311 in the main scanning
direction (a direction orthogonal to the paper plane of FIG.
2).
[0051] The upper wall 312 of the housing 31 has a large rectangular
aperture 317 in plan view at a position corresponding to the
document reading position for the document 6 to be read in the
second reading mode. In the aperture 317, a transparent document
table 83 (platen glass) is disposed to support the document 6. A
portion of the document table 83 on the side of the DADF 33 has a
transparent reading window 79 through which the document 6 is read
in the first reading mode. Between the reading window 79 and the
document table 83, a guide member 84 having an inclined upper end
surface is provided to guide the document 6 to the transport roller
75 after the document 6 passes through the reading position in the
first reading mode.
[0052] The image reading device 3 includes, inside the housing 31,
an image reading section composed of a light source 85, a reflector
86, a first mirror 87, a second mirror 88, a third mirror 89, and
an imaging lens 91. The light source 85 serves as an illumination
unit, such as an illumination lamp or a light emitting diode (LED),
which radiates light for illuminating the document 6. The reflector
86 reflects a part of the light emitted from the light source 85
toward a document 6. The first mirror 87 receives reflected light
from the document 6. The second mirror 88 receives reflected light
from the first mirror 87. The third mirror 89 receives reflected
light from the second mirror 88. The imaging lens 91 focuses
reflected light from the third mirror 89 onto an image reading
element 90 serving as an example of an image reading unit such as a
charge-coupled device (CCD) or a complementary metal oxide
semiconductor (CMOS). The light source 85 radiates light toward the
document 6 and the reflector 86. The first to third mirrors 87 to
89 and the imaging lens 91 constitute a reading optical system that
reads an image on the document 6 with the image reading element
90.
[0053] The light source 85, the reflector 86, and the first mirror
87 are arranged in the main scanning direction, and are mounted in
a first moving body 92 formed by a carriage that can be moved in
the sub-scanning direction by a driving unit. The first moving body
92 illuminates a reading target region on the document 6 while
moving along a first rail 93 in the sub-scanning direction and
reflects reflected light from the document 6 toward the second
mirror 88 in a second moving body 94 by using the first mirror 87.
The first rail 93 is disposed on the rear wall 316 of the housing
31 to extend in the sub-scanning direction.
[0054] The second mirror 88 and the third mirror 89 are arranged in
the main scanning direction, and are mounted in a second moving
body 94 formed by a carriage that can be moved by the driving unit
in the sub-scanning direction. The second moving body 94 reflects
reflected light from the document 6 toward the imaging lens 91 in
the image reading section while moving in the sub-scanning
direction along a second rail 95. The second rail 95 is disposed on
the bottom wall 313 of the housing 31 to extend in the sub-scanning
direction. The single first rail 93 and the single second rail 95
are arranged to be opposed to opposite end portions in the main
scanning direction.
[0055] The image reading section includes an image reading
substrate 97 on which the image reading element 90 is mounted. The
imaging lens 91 and the image reading substrate 97 are attached to
a base plate 96 supported by the bottom wall 313. In the image
reading section, reflected light from the third mirror 89 passes
through the imaging lens 91 and is focused on the image reading
element 90 such as a CCD or a CMOS, an image on the document 6 is
read by the image reading element 90, and image data is output. The
image data read by the image reading element 90 is subjected to a
predetermined image processing, such as shading correction, by an
unillustrated image processing device as required, and is then
transmitted to the control device 100.
[0056] In the first reading mode, as shown by a solid line in FIG.
2, documents 6 are automatically transported by the DADF 33 in a
state in which the first and second moving bodies 92 and 94 are
stopped at the reading position set at the left end of the housing
31, a document 6 passing over the reading window 79 is illuminated
by the light source 85, and a reflected light image from the
document 6 is reflected by the first mirror 87 toward the imaging
lens 91 via the second and third mirrors 88 and 89. In the image
reading section, the reflected light image from the third mirror 89
is focused on the image reading element 90 by the imaging lens 91,
the image on the document 6 is read by the image reading element
90, and image data is output from the image reading element 90.
[0057] In contrast, in the second reading mode, the first moving
body 92 and the second moving body 94 are driven by the
unillustrated driving unit. The moving amount of the second moving
body 94 is set to be half of the moving amount of the first moving
body 92 so that the optical path length from the image reading
position for the document 6 to the image reading element 90 does
not change during movement of the first moving body 92 in the
sub-scanning direction. In FIG. 2, two-dot chain lines show the
positions of the first moving body 92 and the second moving body 94
when the first moving body 92 is moved near an end portion in the
sub-scanning direction for the document 6.
Structure of Principal Part of Image Reading Device
[0058] As illustrated in FIG. 3, the image reading device 3
according to the first exemplary embodiment includes a sheet
transport device 320 that loosens and transports documents 6
serving as an example of a sheet stored in the document storage
unit 70 one by one to the reading position and that transports a
document 6 having passed through the reading position to the
reading position again in a state in which the document 6 is
inverted by being switched back and then outputs the document 6.
The sheet transport device 320 includes the nudger roller 71, the
feed roller 72, the pressure pad 72a, the first transport roller
73, the transport rollers 74 and 75, the output roller 77, a single
driving source 321, a fixed-direction rotation mechanism 322, a
first driving transmission switch unit 323, and a second driving
transmission switch unit 324. The driving source 321 serves as an
example of a driving unit for driving these rollers. The
fixed-direction rotation mechanism 322 serves as an example of a
rotating unit that rotates the first transport roller 73 in a fixed
direction regardless of the rotating direction of the driving motor
321. The first driving transmission switch unit 323 serves as an
example of a switch unit that switches between states in which the
driving force is transmitted to the first transport roller 73 and
is not transmitted thereto. The second driving transmission switch
unit 324 serves as an example of a switch unit that switches
between states in which the driving force is transmitted to the
feed roller 72 and the nudger roller 71 and is not transmitted
thereto.
[0059] As illustrated in FIG. 3, the sheet transport device 320
includes a normal transport path 325 that transports the document 6
transported by the nudger roller 71 so that the document 6 passes
through the feed roller 72, the first transport roller 73, the
transport rollers 74 and 75, and the output roller 77, and an
inverting transport path 326 that transports the document 6, which
is held at a trailing edge by the output roller 77, to the first
transport roller 73 again in a state in which the document 6 is
inverted by reversing the rotating direction of the output roller
77. The normal transport path 325 includes plural guide members
325a and 325b divided along the normal transport path 325 to guide
the front and back surfaces of the document 6, the reading guide
78, and the back-surface support member 80. The inverting transport
path 326 includes guide members 326a and 326b that guide the front
and back surfaces of the document 6.
[0060] At a branch position where the normal transport path 325 and
the inverting transport path 326 separate from each other, a switch
gate 327 is provided to switch the transport path of the document 6
from the normal transport path 325 to the inverting transport path
326. For example, the switch gate 327 is formed by an elastically
deformable synthetic resin film having a substantially Y-shaped
cross section. As illustrated in FIG. 3, the switch gate 327 is
usually disposed so that a part thereof obliquely crosses the
normal transport path 325. When the document 6 is transported to
the output roller 77 along the normal transport path 325, the
switch gate 327 is pushed and elastically deformed by the document
6 to open the normal transport path 325 and to switch the transport
direction of the document 6 toward the output roller 77. On the
other hand, when the document 6 is transported to the inverting
transport path 326 by reversing the rotating direction of the
output roller 77 while the output roller 77 holds the trailing edge
of the document 6, the switch gate 327 switches the transport path
of the document 6 transported by the output roller 77 from the
normal transport path 325 to the inverting transport path 326.
[0061] The sheet transport device 320 includes a document sensor
328 provided at a position corresponding to the nudger roller 71 to
detect a leading edge of the document 6. The sheet transport device
320 further includes a pre-registration sensor 329 provided
upstream of the first transport roller 73 in the transport
direction of the document 6 to detect the leading edge of the
document 6.
[0062] The structure of the sheet transport device 320 will be
described more specifically. As illustrated in FIGS. 4 and 5, the
sheet transport device 320 includes a driving motor 321 serving as
an example of a driving unit. The driving motor 321 is configurated
so that the rotating direction thereof can be switched between a
first direction (forward direction) and a second direction (reverse
direction). An output gear 332 is attached to an output shaft 331
of the driving motor 321 (see FIG. 5). The output gear 332 rotates
in first and second directions R1 and R2 in accordance with the
rotating direction of the driving motor 321. The output gear 332 is
meshed with a first idler gear 333a of an integral double idler
gear 333. A first driving gear 334 for rotating the first transport
roller 73 and the transport rollers 74 and 75 is meshed with a
second idler gear 333b of the double idler gear 333. A sun gear 335
is provided integrally with one axial side of the first driving
gear 334, and a driving pulley 336 is provided integrally with the
other axial side of the first driving gear 334.
[0063] As illustrated in FIG. 6, the first driving gear 334, the
sun gear 335, and the driving pulley 336 are rotatably attached to
a support shaft 399 laid between first and second frames 397 and
398 of the sheet transport device 320. As illustrated in FIGS. 4
and 5, a driving belt 338 is wound on the driving pulley 336.
Further, the driving belt 338 is stretched on a tension pulley 339
that applies tension to the driving belt 338, a driven pulley 341
attached to one end portion of a rotation shaft 340 of the
transport roller 74, a driven pulley (not illustrated) that changes
the stretching direction of the driving belt 338, and a driven
pulley 343 (see FIG. 5) attached to one end portion of a rotation
shaft 342 of the transport roller 75. Referring to FIG. 6, a coil
spring S applies tension to the tension pulley 339.
[0064] As illustrated in FIGS. 5 and 7, first and second planet
gears 344 and 345 having a diameter smaller than that of the sun
gear 335 are meshed with the outer periphery of the sun gear 335.
The first and second planet gears 344 and 345 are rotatably
attached to distal end portions of a planet carrier 346 that is
rotatably mounted on the support shaft 399 of the sun gear 335. The
first and second planet gears 344 and 345 are arranged so that the
center angle on the side of a one-direction gear 348 (to be
described later) is smaller than 180 degrees. The planet carrier
346 is pressed against a side surface of the sun gear 335 with a
required pressure by an annular leaf spring 347 having a curved
side surface (see FIG. 4). The planet carrier 346 rotates in the
same direction as the rotating direction of the sun gear 335 along
with the rotation of the sun gear 335.
[0065] As illustrated in FIG. 4, a one-direction gear 348 serving
as an example of a one-direction gear part to be selectively meshed
with the first or second planet gear 344 or 345 is provided beside
the sun gear 335. The one-direction gear 348 is rotatably mounted
on a rotation shaft 349 of the first transport roller 73. When the
sun gear 335 rotates in the forward direction (clockwise direction
in FIG. 4), the one-direction gear 348 is rotated in the clockwise
direction in FIG. 4 by being directly meshed with the first planet
gear 344 attached to the planet carrier 346. Further, when the sun
gear 335 rotates in the reverse direction (counterclockwise
direction in FIG. 4), the one-direction gear 348 is similarly
rotated in the clockwise direction by being meshed with the second
planet gear 345 attached to the planet carrier 346 with an
intermediate gear 351 being disposed therebetween. In this way, the
one-direction gear 348 constantly rotates in the fixed direction
(clockwise direction in FIG. 4), regardless of the rotating
direction of the driving motor 321 for driving the sun gear 335 in
the forward direction and the reverse direction. The sun gear 335,
the first and second planet gears 344 and 345, the intermediate
gear 351, and the one-direction gear 348 constitute a
fixed-direction rotation mechanism 322.
[0066] As illustrated in FIGS. 5 and 7, the intermediate gear 351
is rotatably attached to a distal end 352a of an arm member 352.
The intermediate gear 351 is constantly meshed with the
one-direction gear 348. The arm member 352 is attached to the
support shaft 399 in a fixed state. As illustrated in FIG. 6, the
arm member 352 is disposed between the second frame 398 and the
planet carrier 346. As described above, the planet carrier 346 is
pressed against the side surface of the sun gear 335 by the annular
leaf spring 347 interposed between the planet carrier 346 and the
arm member 352. Columnar projections 346a and 346b provided on the
planet carrier 346 are in contact with side surfaces 352b and 352c
of a support portion that rotatably supports the first and second
planet gears 344 and 345 in the arm member 352. Thus, the planet
carrier 346 that rotates together with the sun gear 335 is
positioned. The intermediate gear 351 is coaxially provided with a
driven pulley (not illustrated) that changes the stretching
direction of the driving belt 338. The intermediate gear 351 serves
to transmit the rotation to the one-direction gear 348 by reversing
the rotating direction of the second planet gear 345. The
intermediate gear 351 does not always need to be a single gear, and
may be composed of an odd number of intermediate gears meshed with
one another.
[0067] In the first exemplary embodiment, the same gears are used
as the first and second planet gears 344 and 345 and the
intermediate gear 351 in order to use parts in common.
[0068] As illustrated in FIG. 4, the one-direction gear 348 is
attached to a first electromagnetic clutch 323 serving as an
example of a first driving transmission switch unit. As illustrated
in FIG. 8, the first electromagnetic clutch 323 includes a rotor
323a, a stator 323c, an armature 323d, an excitation coil 323e, and
a cylindrical exterior 323f. The rotor 323a is fixed to the
rotation shaft 349 of the first transport roller 73 with a D-cut
surface 349a provided on the rotation shaft 349 being disposed
therebetween. The stator 323c is fixed to the rotor 323a with a
bearing 323b being disposed therebetween. The armature 323d is
rotatably attached to the rotation shaft 349 and is formed by a
moving piece to which the one-direction gear 348 is fixed. The
excitation coil 323e is provided in the stator 323c to form a
magnetic circuit that penetrates in the axial direction of the
rotor 323a. The exterior 323f also functions as a yoke, and
protects the excitation coil 323e. The exterior 323f is disposed
next to the one-direction gear 348. The outer diameter of the
exterior 323f is set to be larger than that of the one-direction
gear 348. The exterior 323f may be provided integrally with the
stator 323c. The stator 323c is fixed to the second frame 398 of
the sheet transport device 320 with a whirl stop portion 323g being
disposed therebetween. The armature 323d has an unillustrated
separating spring that biases the armature 323d in a direction to
separate from the rotor 323a. This forms a gap G between a vertical
surface of the armature 323d and a side surface of the rotor
323a.
[0069] In the first electromagnetic clutch 323, the armature 323d
and the rotor 323a are coupled against the separating spring by
supplying power to the excitation coil 323e, and the rotation
driving force of the armature 323d, which is rotated by the
one-direction gear 348, is transmitted to the rotor 323a to rotate
the rotation shaft 349 to which the rotor 323a is fixed.
[0070] On the other hand, in the first electromagnetic clutch 323,
the armature 323d is separated from the rotor 323a by elastic force
of the separating spring by stopping the supply of power to the
excitation coil 323e, the rotation driving force of the armature
323d is not transmitted to the rotor 323a, and the rotation shaft
349 to which the rotor 323a is fixed is stopped. At this time, the
armature 323d to which the one-direction gear 348 is attached
continues rotation together with the one-direction gear 348.
[0071] As illustrated in FIG. 5, a second driving gear 355 for
rotating the nudger roller 71, the feed roller 72, and the output
roller 77 is meshed with the second idler gear 333b of the double
idler gear 333. The second driving gear 355 is meshed with a driven
gear 357 attached to an end portion of a rotation shaft 356 of the
output roller 77. Further, as illustrated in FIG. 4, a transmission
gear 358 for transmitting the rotation driving force to the nudger
roller 71 and the feed roller 72 is meshed with the driven gear
357. To a rotation shaft 359 of the transmission gear 358, a second
electromagnetic clutch 324 is attached as an example of a second
driving transmission switch unit. The second electromagnetic clutch
324 has a structure similar to that of the first electromagnetic
clutch 323. Referring to FIG. 4, the second electromagnetic clutch
324 has a whirl stop portion 324g.
[0072] As illustrated in FIG. 4, a driven gear 360 formed by a
helical gear or a spur gear is fixed to the rotation shaft 359 of
the transmission gear 358. A transmission gear 361 similarly formed
by a helical gear or a spur gear to transmit the rotation driving
force to the feed roller 72 is also meshed with the driven gear
360.
[0073] In the first exemplary embodiment, as illustrated in FIG. 5,
a release unit 362 is provided to release the transport force of
the output roller 77 for the document 6 at a preset timing when the
rotating direction of the driving motor 321 is switched to the
forward direction after the output roller 77 transports the
document 6 to the first transport roller 73 by switching back the
document 6.
[0074] As illustrated in FIG. 3, the release unit 362 is
configurated to separate upper driven rollers 77a, of the output
roller 77 composed of a pair of rollers in pressure contact with
each other, from lower driving rollers 77b. As illustrated in FIG.
9, the driven rollers 77a of the output roller 77 are rotatably
attached to distal ends of arms 364 extending from a support shaft
363 rotatably supported by the sheet transport device 32 in an
intersecting direction. A lift arm 365 for lifting the driven
rollers 77a in a direction to separate from the driving rollers 77b
is provided integrally with one end portion of the support shaft
363 in a direction intersecting the support shaft 363. As
illustrated in FIG. 5, the lift arm 365 is moved up and down by
intermittent transmission of driving force from the driven gear
357.
[0075] As illustrated in FIGS. 4 and 5, a tooth-lacking gear 367 in
which teeth are not provided in a part thereof in the
circumferential direction is disposed on one side of the driven
gear 357. As illustrated in FIG. 10, the tooth-lacking gear 367 is
formed by coaxially combining a first tooth-lacking gear 368 and a
second tooth-lacking gear 369. As illustrated in FIG. 5, a solenoid
370 is disposed on one side of the tooth-lacking gear 367 to
intermittently drive the tooth-lacking gear 367.
[0076] As illustrated in FIG. 10, the first tooth-lacking gear 368
includes a cylindrical large-diameter portion 371 having a
relatively large outer diameter, and a small-diameter portion 372
provided integrally with one axial end of the large-diameter
portion 371 and shaped like a hollow cylinder having an outer
diameter relatively smaller than that of the large-diameter portion
371. On the outer periphery of the large-diameter portion 371, a
first gear portion 373 and a second gear portion 374 that form a
center angle smaller than 180 degrees are provided at positions
symmetrical with respect to the center of the axis. Between the
first gear portion 373 and the second gear portion 374, a first
tooth-lacking portion 375 and a second tooth-lacking portion 376
are provided so that teeth are not formed therein. On the outer
periphery of the small-diameter portion 372, two engaging portions
377 and 378 are provided at positions spaced 180 degrees apart. As
illustrated in FIG. 5, the engaging portions 377 and 378
respectively include engaging surfaces 377a and 378a provided in
the radial direction and inclined surfaces 377b and 378b inclined
from distal ends of the engaging surfaces 377a and 378a to one side
in the circumferential direction. When the solenoid 370 is in an
off state, a distal end 379a of an operating lever 379 biased by a
spring 370a engages with the engaging portion 377 or 378 of the
small-diameter portion 372, as illustrated in FIG. 5.
[0077] In contrast, as illustrated in FIG. 10, the second
tooth-lacking gear 369 includes a cylindrical large-diameter
portion 380 having a relatively large outer diameter, and a cam
portion 381 provided integrally with one axial end of the
large-diameter portion 380. Similarly to the first tooth-lacking
gear 368, on the outer periphery of the large-diameter portion 380,
a third gear portion 382 and a fourth gear portion 383 that form a
center angle smaller than 180 degrees are provided at positions
symmetrical with respect to the center of the axis. Between the
third gear portion 382 and the fourth gear portion 383, a third
tooth-lacking portion 384 and a fourth tooth-lacking portion 385
are provided. The third and fourth gear portions 382 and 383 and
the third and fourth tooth-lacking portions 384 and 385 are
structured similarly to the first and second gear portions 373 and
374 and the first and second tooth-lacking portions 375 and 376,
respectively.
[0078] The cam portion 381 includes a first flat portion 381a
shaped like a flat surface at a position near the rotation axis, a
second flat portion 381b shaped like a flat surface at a position
farther from the rotation axis than the first flat portion 381a,
and curved portions 381c and 381d that connect the first and second
flat portions 381a and 381b.
[0079] Between the first tooth-lacking gear 368 and the second
tooth-lacking gear 369, a coil spring 386 is provided as an example
of a rotation-force applying part that applies rotation force for
rotating the first tooth-lacking gear 368 relative to the second
tooth-lacking gear 369 in the clockwise direction in FIG. 5. One
end of the coil spring 386 is inserted in an insertion hole 387 of
the first tooth-lacking gear 368. The other end of the coil spring
386 is inserted in an insertion hole 388 of the second
tooth-lacking gear 369 (see FIG. 11).
[0080] A pin 389 serving as a guided member is provided on a side
surface of the second tooth-lacking gear 369 facing the first
tooth-lacking gear 368. On the other hand, a guide groove 390
serving as an example of a guide portion is provided in the first
tooth-lacking gear 368 in correspondence with the pin 389. The
guide groove 390 is arc-shaped to form a required center angle at a
required position around the axis. In a state in which the first
tooth-lacking gear 368 and the second tooth-lacking gear 369 are
combined, the coil spring 386 applies rotation force for rotating
the first tooth-lacking gear 368 relative to the second
tooth-lacking gear 369 in the clockwise direction in FIG. 5. In the
state of FIG. 5, the pin 389 is located in one end portion 390a of
the guide groove 390.
[0081] As illustrated in FIG. 9, a distal end portion 392 of an
operating member 391 is disposed to be constantly held in pressure
contact with the cam portion 381 of the second tooth-lacking gear
369 by elastic force of an unillustrated coil spring or the like.
The operating member 391 is turnably attached to the first frame
397 with a support shaft 393 provided at its base end portion being
disposed therebetween. An operating portion 394 for moving the lift
arm 365 up and down protrudes from a side surface of the base end
portion of the operating member 391 in the axial direction of the
support shaft 393. At a distal end of the operating member 391, a
planar detector 395 is provided to detect the position of the
operating member 391 with a position sensor 396.
[0082] As illustrated in FIG. 11A, in the release unit 362, the
solenoid 370 is usually in an off state, and the operating lever
379 is engaged with one engaging portion 377 of the tooth-lacking
gear 367. At this time, the tooth-lacking gear 367 is stopped at a
position where the second and fourth tooth-lacking portions 376 and
385 are opposed to the driven gear 357. For this reason, the
rotation driving force of the driven gear 357 is not transmitted to
the tooth-lacking gear 367. The first flat portion 381a of the cam
portion 381 in the tooth-lacking gear 367 is in contact with the
distal end portion 392 of the operating member 391. Hence, the
operating member 391 is located at a position turned in the
counterclockwise direction in FIG. 9. For this reason, the
operating portion 394 of the operating member 391 is turned
downward, the lift arm 365 is pushed down, and the driven rollers
77a of the output roller 77 are in contact with the driving rollers
77b.
[0083] Next, as illustrated in FIG. 11B, in the release unit 362,
when the solenoid 370 is made in an on state only in a preset short
time, the engaged state between the distal end 379a of the
operating lever 379 and the engaging portion 377 of the
tooth-lacking gear 367 is released. Then, the first tooth-lacking
gear 368 of the tooth-lacking gear 367 is rotated by the elastic
force of the coil spring 386, and the first gear portion 373 of the
first tooth-lacking gear 368 is meshed with the driven gear 357.
For this reason, the first tooth-lacking gear 368 is rotated in the
counterclockwise direction in FIG. 11B by the driven gear 357. At
this time, the second tooth-lacking gear 369 is stopped. When the
first tooth-lacking gear 368 rotates a required angle or more in
the counterclockwise direction in FIG. 11B, the pin 389 of the
second tooth-lacking gear 369 comes into contact with an end
portion 390b of the guide groove 390 in the first tooth-lacking
gear 368, as illustrated in FIG. 10. As a result, the second
tooth-lacking gear 369 is rotated in the same direction a required
angle behind the first tooth-lacking gear 368, and the third gear
portion 382 is meshed with the driven gear 357.
[0084] When the first tooth-lacking gear 368 rotates to a position
where engagement of the first gear portion 373 and the driven gear
357 is finished and the first tooth-lacking portion 375 is opposed
to the driven gear 357, as illustrated in FIG. 12A, the rotation
driving force is not transmitted from the driven gear 357. However,
the elastic force in the clockwise direction in FIG. 5 is applied
from the coil spring 386 to the first tooth-lacking gear 368. For
this reason, the first tooth-lacking gear 368 continues the
rotation in the clockwise direction in FIG. 5, and is stopped in a
state in which the other engaging portion 378 is engaged with the
distal end 379a of the operating lever 379 in the solenoid 370, as
illustrated in FIG. 12B.
[0085] In contrast, as described above, the second tooth-lacking
gear 369 rotates in the same direction as the first tooth-lacking
gear 368 the required angle behind the first tooth-lacking gear
368. For this reason, at the time when the second tooth-lacking
gear 369 rotates to a position where the first tooth-lacking
portion 375 of the first tooth-lacking gear 368 is opposed to the
driven gear 357, it continues the rotation while the third gear
portion 382 is still meshed with the driven gear 357.
[0086] After that, as illustrated in FIG. 12B, the second
tooth-lacking gear 369 rotates to a position where the engagement
between the third gear portion 382 and the driven gear 357 is
finished and the third tooth-lacking portion 384 is opposed to the
driven gear 357. Then, the rotation driving force is not
transmitted from the driven gear 357 to the second tooth-lacking
gear 369. At this time, the cam portion 381 of the second
tooth-lacking gear 369 is set to be brought into pressure contact
with the distal end portion 392 of the operating member 391 between
the curved portion 381d and the second flat portion 382b after
passing through a dead center where the eccentricity amount of the
cam portion 381 is the largest. For this reason, at the time when
engagement of the third gear portion 382 and the driven gear 357 is
finished, rotational moment for rotating the second tooth-lacking
gear 369 in the counterclockwise direction in FIG. 12A is applied
to the second tooth-lacking gear 369 by the pressing force between
the second flat portion 382b of the cam portion 381 and the distal
end portion 392 of the operating member 391. As a result, as
illustrated in FIG. 12B, the second tooth-lacking gear 369 rotates
and stops at a position where the entire surface of the second flat
portion 381b of the cam portion 381 is in pressure contact with the
distal end portion 392 of the operating member 391.
[0087] At this time, the distal end portion 392 of the operating
member 391 is pushed down by the cam portion 381 of the second
tooth-lacking gear 369. In FIG. 9, the operating member 391 is at a
position where it is rotated in the clockwise direction. For this
reason, the operating portion 394 of the operating member 391 turns
upward and pushes up the lift arm 365. The support shaft 363
provided with the lift arm 365 rotates in the counterclockwise
direction in FIG. 9. Therefore, the driven rollers 77a of the
output roller 77 move to a position separate from the driving
rollers 77b.
[0088] In the tooth-lacking gear 367, the first tooth-lacking gear
368 first stops, and the second tooth-lacking gear 369 rotates in
the same direction as the first tooth-lacking gear 368 after some
delay and stops. In the meantime, the coil spring 386 is tightened
by the second tooth-lacking gear 369 that rotates relative to the
stopped first tooth-lacking gear 368.
[0089] After that, the tooth-lacking gear 367 is rotated 180
degrees by bringing the solenoid 370 into an on state only for a
preset time and returns to the state of FIG. 11A, and the driven
rollers 77a of the output roller 77 come into contact with the
driving rollers 77b.
[0090] In this way, in the release unit 362, the operating member
391 is turned by turning the solenoid 370 on and off, the driven
rollers 77a of the output roller 77 are separated from the driving
rollers 77b, and the state in which the transport force of the
output roller 77 acts on the document 6 is released.
[0091] As illustrated in FIGS. 13A and 13B, the first planet gear
344 in the first exemplary embodiment is provided with a
displacement-force applying part that applies a force for
displacing the first planet gear 344 in a direction to mesh with
the one-direction gear 348 when an end portion of the outer
periphery in the axial direction of the first planet gear 344
touches the outer periphery of the first electromagnetic clutch
323.
[0092] More specifically, in the sheet transport device 320, when
the sun gear 335 rotates in the clockwise direction in FIG. 7, the
planet carrier 346 in pressure contact with the sun gear 335 turns
in the same direction, and the first planet gear 344 rotatably
attached to the planet carrier 346 is meshed with the one-direction
gear 348. At this time, as illustrated in FIG. 6, when the
thickness of the first planet gear 344 is taken as X and the
thickness of the sun gear 335 is taken as Y, a gap A (=Y-X) is set
between the sun gear 335 and the first planet gear 344. In this
case, the thickness X of the first planet gear 344 and the
thickness Y of the sun gear 335 have tolerances .alpha. and .beta.
including attachment errors, respectively. Therefore, the gap A
between the sun gear 335 and the first planet gear 344 is set to be
more than or equal to the tolerances (.alpha.+.beta.) of the first
planet gear 344 and the sun gear 335. The attachment position of
the one-direction gear 348 also has a tolerance in the axial
direction with respect to the second frame 398.
[0093] For this reason, when the planet carrier 346 turns in the
clockwise direction in FIG. 7 and the first planet gear 344 meshes
with the one-direction gear 348, the first planet gear 344 may
touch the exterior 323f of the first electromagnetic clutch 323
along the axial direction of the first planet gear 344 without
meshing with the one-direction gear 348, as illustrated in FIG. 14.
If the outer peripheral end of the first planet gear 344 touches
the exterior 323f of the first electromagnetic clutch 323, the
rotation driving force is not transmitted from the first planet
gear 344 to the one-direction gear 348, and the first transport
roller 73 is not rotated. In this case, transport failure of the
first transport roller 73 for the document 6 occurs.
[0094] Accordingly, in the first exemplary embodiment, as
illustrated in FIGS. 13A and 13B, at least axial end portions (both
end portions in the illustrated example) of gear tooth tips on the
side of the first electromagnetic clutch 323 at an outer peripheral
edge 344a of the first planet gear 344 have chamfered (so-called
C-cut) portions 344b that are cut at an inclination of 45 degrees
to serve as an example of a displacement-force applying part. For
example, the first planet gear 344 is produced by injection molding
using a synthetic resin material such as POM. At this time, a
molding die for injection molding of the first planet gear 344 has
chamfered portions 344b formed beforehand at positions
corresponding to the both axial end portions of the tooth tips.
Thus, the chamfered portions 344b are formed in the first planet
gear 344 simultaneously with injection molding. As described above,
it is only necessary that the first planet gear 344 should have the
chamfered portions 344b at least only at the outer peripheral end
opposed to the first electromagnetic clutch 323. In the first
exemplary embodiment, however, the chamfered portions 344b are
provided at both axial end portions of the first planet gear 344,
that is, the chamfered portions 344b are also provided at the outer
peripheral end that is not opposed to the first electromagnetic
clutch 323 in order to cope with automatic assembly and the like by
eliminating the directivity in the axial direction of the first
planet gear 344.
[0095] In the first exemplary embodiment, as described above, the
same gears are used as the first and second planet gears 344 and
345 and the intermediate gear 351 in order to use parts in common.
For this reason, chamfered portions are provided not only in the
first planet gear 344 but also in the second planet gear 345 and
the intermediate gear 351.
[0096] For this reason, even when the first planet gear 344 touches
the exterior 323f of the first electromagnetic clutch 323 without
meshing with the one-direction gear 348, the chamfered portions
344b of the first planet gear 344 touch the exterior 323f of the
first electromagnetic clutch 323. As a result, in the chamfered
portions 344b of the first planet gear 344, a displacement force F2
equal to a contact force F1 with which the first planet gear 344
touches the exterior 323f of the first electromagnetic clutch 323
acts toward the one-direction gear 348, as illustrated in FIG.
15.
Operations of Characteristic Parts of Image Forming Apparatus
[0097] In the image reading device 3 of the first exemplary
embodiment, images on the front surface and the back surface of the
document 6 are read as follows.
[0098] That is, in the image reading device 3, as illustrated in
FIG. 3, the nudger roller 71, the feed roller 72, and so on are
driven by the driving motor 321, and documents 6 stored in the
document storage unit 70 are transported one by one. At this time,
as illustrated in FIG. 16-1, the first electromagnetic clutch 323
is in an off state, and the first transport roller 73 is stopped. A
document 6 transported by the feed roller 72 is corrected for skew
by the contact of its leading edge with the stopped first transport
roller 73.
[0099] At this time, in the image reading device 3, when the
driving motor 321 is rotated in the forward direction R1, as
illustrated in FIGS. 4 and 5, the first planet gear 344 meshed with
the sun gear 335 moves toward the one-direction gear 348 along with
the rotation of the driving motor 321. At this time, as illustrated
in FIG. 13A, the outer peripheral end 344a of the first planet gear
344 sometimes touches the exterior 323f of the first
electromagnetic clutch 323, for example, owing to the tolerance of
the first planet gear 344. At this time, as illustrated in FIGS.
13A and 13B, the chamfered portions 344b are provided at the axial
ends of the outer peripheral end 344a of the first planet gear 344.
For this reason, even when the outer peripheral end 344a of the
first planet gear 344 touches the exterior 323f of the first
electromagnetic clutch 323, the displacement force F2 in the
direction to mesh with the one-direction gear 348 is applied to the
first planet gear 344 by the chamfered portions 344b provided in
the first planet gear 344, as illustrated in FIG. 15. Therefore,
even when the outer peripheral end 344a of the first planet gear
344 touches the exterior 323f of the first electromagnetic clutch
323, the first planet gear 344 is displaced in the direction to
mesh with the one-direction gear 348, and meshes with the
one-direction gear 348.
[0100] After that, as illustrated in FIGS. 16-2 and 16-3, when the
first electromagnetic clutch 323 is turned on, the rotation driving
force of the one-direction gear 348 is transmitted to the rotation
shaft 349 of the first transport roller 73, and the first transport
roller 73 transports the document 6 to the transport rollers 74 and
75. An image on the first surface of the document 6 is read by the
image reading element 90 stopped at the first reading position in
the image reading section while it is passing over the reading
window 79, as illustrated in FIG. 2. After that, the document 6 is
output onto the output storage unit 76 by the output roller 77 in
the case of one-sided reading.
[0101] When images on both surfaces of the document 6 are to be
read by the image reading device 3, as illustrated in FIG. 16-4,
the driving motor 321 is rotated in the reverse direction R2 while
the output roller 77 holds a trailing edge of the document 6. When
the driving motor 321 is rotated in the reverse direction R2, the
transport rollers 74 and 75 driven by the driving motor 321 also
rotate in the reverse direction R2. On the other hand, while the
first transport roller 73 is rotated in one direction by the
fixed-direction rotation mechanism 322, it is stopped by turning
off the first electromagnetic clutch 323.
[0102] As illustrated in FIGS. 16-4 and 16-5, the document 6
transported in the reverse direction by the output roller 77 is
transported to the inverting transport path 326 via the switch gate
327 with its front and back surfaces being inverted. By turning on
the first electromagnetic clutch 323 after the leading edge of the
document 6 reaches the first transport roller 73, the first
transport roller 73 is rotated to correct skew of the document 6.
The document 6 is transported to the transport roller 74 by the
rotated first transport roller 73. At this time, the transport
roller 74 is rotated in the reverse direction by the driving motor
321.
[0103] Next, as illustrated in FIG. 16-6, the rotating direction of
the driving motor 321 is switched to the forward direction R1
before the leading edge of the document 6 reaches the transport
roller 74. After being transported to the reading position by the
transport roller 74 rotating in the forward direction R1, the
document 6 is transported to the output roller 77 via the transport
roller 75. At this time, the rotating direction of the output
roller 77 is switched to the forward direction R1 (output
direction) along with the switch of the rotating direction of the
driving motor 321. For this reason, when the leading edge of the
document 6 is held by the first transport roller 73 via the
inverting transport path 326, the document 6 may be pulled in
opposite directions between the first transport roller 73 and the
output roller 77 driven in the output direction. Hence, in the
first exemplary embodiment, the solenoid 370 of the release unit
362 is turned on simultaneously with switching of the rotating
direction of the driving motor 321 from the reverse direction R2 to
the forward direction R1 so that the driven rollers 77a are
separated from the driving rollers 77b in the output roller 77 to
release the transport force of the output roller 77 for the
document 6. This prevents the document 6 from being pulled between
the first transport roller 73 and the output roller 77.
[0104] After that, as illustrated in FIGS. 16-7 and 16-8, the first
document 6 is output by the output roller 77, and transport of the
second document 6 is started.
[0105] In this way, in the first exemplary embodiment, even when
the outer periphery of the first planet gear 344 touches the
exterior 323f of the first electromagnetic clutch 323, as
illustrated in FIGS. 13A and 13B, the displacement force F2 in the
direction to mesh with the one-direction gear 348 acts on the first
planet gear 344. Hence, the first planet gear 344 is meshed with
the one-direction gear 348, and the document 6 is transported by
the driving force reliably transmitted from the driving motor 321
to the one-direction gear 348.
Second Exemplary Embodiment
[0106] FIG. 17 is a structural view illustrating the outline of a
sheet transport device according to a second exemplary embodiment
of the present invention.
[0107] In the second exemplary embodiment, as illustrated in FIG.
17, a chamfered portion 323h serving as an example of a
displacement-force applying part is provided in an axial end
portion of an exterior 323f of a first electromagnetic clutch 323
on the side of a one-direction gear 348.
[0108] Therefore, in the second exemplary embodiment, even when the
outer periphery of a first planet gear 344 touches the exterior
323f of the first electromagnetic clutch 323, a displacement force
in the direction to mesh with the one-direction gear 348 is applied
to the first planet gear 344 by the chamfered portion 323h provided
in the axial end portion of the exterior 323f of the first
electromagnetic clutch 323.
[0109] The foregoing description of the exemplary embodiments of
the present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiments were chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
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